The Academy Awards strive to highlight the most significant annual achievements in acting, the craft of making movies and, for some reason, which song from the last year was pretty good. Yes, the Oscar for best original song is a chance to look back on the small batch of tunes explicitly written for the medium of film. But that’s the problem; it’s a relatively small batch compared with the almost endless number of movies and actors the academy can choose from. It’s not a recipe for consistent excellence.

There are a few kinds of songs that show up repeatedly over the years. You’ve got the mediocre song added to the film adaptation of a beloved stage musical;“Suddenly” from “Les Miserables,” “Learn to Be Lonely” from “The Phantom of the Opera,” “I Move On” from “Chicago,” “Hopelessly Devoted to You” from “Grease” and “Mean Green Mother From Outer Space” from “Little Shop of Horrors.”

‘>¹ one of the Disney, Pixar or Bond songs; or the song that wins but isn’t even the best tune from that movie.Looking at you, “La La Land.”

‘>² There are many years when the obviously superior song — “I Don’t Want to Miss a Thing,” “The Power of Love,” “Eye of the Tiger” or “The Bare Necessities” — loses. My favorite nominees of all are the C to C-minus ballads from extremely popular musicians grasping their best chance to win Oscar gold, such as Bono,“The Hands That Built America”

‘>³ Paul McCartney,“Vanilla Sky”

‘>⁴ Bruce Springsteen,“Dead Man Walkin’,” and “Streets of Philadelphia”

‘>⁵ Jon Bon Jovi,“Blaze of Glory”

‘>⁶ Justin Timberlake“Can’t Stop the Feeling!”

‘>⁷ or, most of all, Sting.“My Funny Friend and Me,” “Until,” “You Will Be My Ain True Love” and “The Empty Chair”

‘>⁸

In other words, I find the best original song category fascinating because its nominees span such a wide range in quality — the most timeless songs in cinema history and songs that prove the music branch will nominate a ham sandwich if Bono or Randy Newman was involved in making it.

So let’s find out the worst best original song. (OK, we’ll find the best one too.) We took a 30-second clip from every best original song winner in Academy Award history and loaded the samples into a random matchup generator. Then we asked people to select which song they preferred. We promoted this across FiveThirtyEight’s social channels over several weeks. It’s not a scientific sample, but with more than 50,000 individual matchups evaluated, I’m confident that this ranking approximates prevailing attitudes toward the winners.Among our readers, at least.

“>⁹ We can then rank each song by the percent of matchups it won.

I was originally worried that the biases of the audience would penalize older songs over more recent songs, but that wasn’t the case; more to the point, it appears that we’re in a bit of a dark age when it comes to movie songs.

The best era for movie songs appears to be the 1980s and 1990s — bracketed by “Fame” in 1980 and “My Heart Will Go On” in 1997. The best 10 consecutive years of best original songs ran from 1986 through 1995, with Disney Renaissance hits combining with bangers like “Take My Breath Away” from “Top Gun” and “Time of My Life” from “Dirty Dancing” to make for an unmatched stretch of good winners.Note: FiveThirtyEight is owned by ESPN, which is partially owned by Disney.

“>¹⁰

But which individual songs could be called the best or worst? At the bottom of the pile, there’s “Sweet Leilani” in 1937, “Buttons and Bows” in 1948 and “On the Atchison, Topeka and the Santa Fe” in 1946 (which Judy Garland sang). The worst performing songs of the past 20 years were “I Need to Wake Up” from “An Inconvenient Truth” (2006) and “Man or Muppet” from “The Muppets” (2011).

There’s a large clump of songs that won around 70 percent of their matchups, give or take 3 percentage points. Call this the great-but-not-best cluster. Then there’s a gap before you get to the truly differentiated tunes. The fourth- and third-ranked songs — “Flashdance (What a Feeling)” from “Flashdance” (1983) and “Can You Feel the Love Tonight” from “The Lion King” (1994), respectively — both won 77 percent of their matchups. The No. 2 song, “When You Wish Upon a Star” from “Pinocchio” (1940), won 80 percent.

But they’re no match for the best best original song of all time: Judy Garland’s rendition of “Somewhere Over the Rainbow,” from 1939’s “The Wizard of Oz,” won 91 percent of its matchups. That’s head and shoulders over the competition.

A series of polls shows record support for stricter gun laws in the U.S., so the FiveThirtyEight Politics podcast team discussed whether the public reaction to the mass shooting at a high school in Parkland, Florida, reflects a turning point in the guns debate. The crew also entertains hypothetical political scenarios in a round of political “Would you rather.”

You can listen to the episode by clicking the “play” button above or by downloading it in iTunes, the ESPN App or your favorite podcast platform. If you are new to podcasts, learn how to listen.

The FiveThirtyEight Politics podcast publishes Monday evenings, with occasional special episodes throughout the week. Help new listeners discover the show by leaving us a rating and review on iTunes. Have a comment, question or suggestion for “good polling vs. bad polling”? Get in touch by email, on Twitter or in the comments.

Graphics by Ella Koeze

Influenza isn’t just widespread — the strains in circulation are also severe. As the following chart illustrates, the share of doctor visits for flu and flu-like illnesses has not been this high since the 2009-10 season, when the flu hit early and hard but then quickly declined. (The flu season typically begins around October, peaks somewhere between December and February and peters out by the end of May.)

Still, there’s some good news out this week. Data released Friday shows that, after a steep and steady rise over the past weeks, doctor visits for flu and flu-like illnesses are finally dropping.

The CDC tracks “flu-like illnesses” because viruses other than influenza, such as respiratory syncytial virus, can provoke flu-like symptoms too. Making a definitive diagnosis requires lab testing that takes time and isn’t done in all cases. But what makes influenza on its own noteworthy is that it can become severe enough to kill you — and there’s a vaccine against it.

Prior to each flu season, researchers try to predict which strains will circulate in the coming year so that they can include these in that season’s vaccine. But some years their predictions are better than others. On Feb. 16, the CDC released its latest data on the effectiveness of this year’s vaccine. The numbers showed that the U.S. flu vaccine’s overall effectiveness was 36 percent, which means that a vaccinated person reduced the risk of getting sick enough with the flu to seek a doctor visit by about one-third.

But the vaccine was only about 25 percent effective against a strain called H3N2, a particularly nasty subtype associated with higher rates of hospitalizations and deaths than other strains. And that’s a problem, because the H3N2 strain has been the most predominant this year. “We see lower protection against the H3N2 strain than we see against others, and that’s a consistent finding from year to year,” said Edward Belongia, an epidemiologist at the Marshfield Clinic Research Institute in Wisconsin who has tracked the vaccine’s effectiveness for the CDC over the past 14 flu seasons. The reasons for this aren’t entirely clear, but there are a few preliminary and puzzling clues:

1. There’s some evidence to suggest that the first flu virus you’re exposed to as a child may orient your immune system to respond best to that kind of flu virus. This suggests that people who were exposed to H3N2 as children may mount a better immune response to it, Belongia said. If that’s true, people older than 50 may be especially vulnerable: “Before 1968, no one was being exposed to H3N2,” he said.
2. Numerous studies going back to the 1970s suggest that people who are vaccinated every year may not get as much protection as those who get the vaccine one year but not the previous one or two years before then. This so-called repeated vaccination effect is not always present, and “we don’t know what’s driving it,” Belongia said. “It’s very complicated and may be different in children than in older adults.”
3. The H3N2 viruses can mutate when grown in eggs for producing the vaccines, and that can lead to meaningful changes in how well the vaccine works, even if it was well-matched to the strains in circulation.

What does this all mean? The flu vaccine is helpful, but it’s not enough to get everyone through the winter without coming down with the crud. Even at the peak of the season, Belongia said, only something like 40 percent to 50 percent of the people who seek care for flu-like symptoms actually have influenza. And until scientists develop a universal flu vaccine that’s effective against all strains, the vaccines we have will only reduce the severity of flu season, not eliminate it.

If we want to get serious about preventing flu deaths — particularly if there’s a pandemic or a dangerous new strain — we should also give serious thought to quarantine strategies. The word quarantine carries a lot of political and ethical baggage, but it doesn’t have to mean restricting travel. It can also include promoting policies that enable people to stay home when they are sick.

People who have the flu are very infectious, and if they can stay home from work or school (and the grocery store and post office and everywhere else), they can reduce the spread of the disease. But our societal and workplace norms can make it hard to stay home when you’re sick. People who have a respiratory illness should avoid passing things like money or food back and forth, and yet workers in jobs that require tasks like these may find it especially hard to get (or afford) time off.

“We have many workplaces where people don’t have an opportunity to take any paid sick leave, so you have a strong incentive to come into work no matter how sick you are,” Belongia said. “I don’t know what the solution is, but this needs to be looked at in terms of sick leave policies.”

As this brutal flu season barrels on, taking precautions to stop its spread remains crucial. In many cases, that can mean avoiding public places when you’re ill. Yes, you can spread the flu in the early stages, before you’re flat-out sick, but you’re particularly contagious when you’re in the thick of the symptoms. And in that case, unless you require urgent medical care, the best thing you can do is stay the hell home.

Stop me if you’ve heard this one before: A mining industry is trapped in a state of slow economic decline and looks to the Trump administration to reverse its fortunes.

That could be the lead-in to a story about coal — an industry the administration has made a point of promoting. But it’s also similar to the story of uranium, the radioactive mineral that serves as a raw material for manufacturing fuel for nuclear power plants and the explosive cores of nuclear weapons. The key difference: Although coal companies have pushed for reduced regulation, representatives of uranium mining companies told me in an interview that they don’t want less environmental protection. They want protection of a different kind, however.

In its efforts to make coal great again, the Trump administration has made a point of embracing the industry, cutting regulations and talking up the mineral’s importance. Uranium hasn’t gotten quite the same level of personal attention from the president. (There’s been a distinct lack of “Trump Digs Uranium” signs, for instance.) But his administration has made several moves in the past year that seem to favor uranium mining interests: It shrunk the Bears Ears National Monument in Utah in a way that would make it easier for companies to mine uranium on hundreds of previously established claims in the area; it proposed ending a ban on uranium mining near the Grand Canyon; it moved forward on a proposed uranium mine near the Black Hills; it nominated a deputy administrator for the Environmental Protection Agency who used to be a lobbyist for a uranium mining company; and it left an Obama-era proposal about groundwater protections at uranium mining sites in limbo — neither approving the proposed rule nor rejecting it.

But while it’s taken outside economists to point out that environmental protection rollbacks aren’t going to save the coal industry, uranium industry insiders say they have little interest in taking advantage of the loosened environmental protections the Trump administration has offered them. “There’s not a big push to start up new mines [on former federal lands]; the price is way too low,” said John Cash, vice president for regulatory affairs at the uranium mining company Ur-Energy. “The market is really oversupplied at this point.” He said uranium mining companies don’t want to roll back environmental regulation. Instead, they’d rather the government block foreign competition.

There was a time when it was good to be a U.S. uranium mining company. During the Cold War, the federal government set up a series of policies that had the effect of guaranteeing uranium miners a high price for their product, said Luke Danielson, president of the Sustainable Development Strategies Group, which consults on minerals development projects around the world. “People made massive amounts of money in this boom,” he said. “But in the mid-’60s, the government realized we had enough uranium stockpiled to last a really long time, and it pulled the plug.” Production rebounded in the 1970s — a time of optimism about the future of nuclear energy — but the output of the U.S. uranium industry has been on the decline since 1980.

That trend continues as old nuclear power plants close and aren’t replaced. Meanwhile, contrary to the collective wisdom of the 20th century, demand for electricity doesn’t seem to have to go up, exponentially, forever. Back then, the industry believed that there would always be new demand and that new power plants would have to be built to meet it, said Nick Carter, executive vice president for uranium at the UX Consulting Co., a nuclear industry data and consulting firm. But demand has stagnated, and the nuclear industry hasn’t had much luck competing, cost-wise, against cheaper natural gas, wind and solar resources. So when utility companies buy nuclear fuel, they are focused on keeping costs low and are looking for the best deal. And that usually isn’t coming from the U.S.

In 2016, just 10 percent of the uranium purchased by the owners of nuclear power plants was domestically sourced. That’s why Cash and Paul Goranson, chief operating officer for Energy Fuels, another uranium mining company, want help on the demand side of the equation. In January, their two companies filed a petition with the U.S. Commerce Department asking for an investigation into whether the industry needs government protection against foreign competitors. Only 14 of these investigations have taken place since 1980, and it’s rarer still for the government to take action. Ultimately, though, Cash and Goranson would like to see the administration mandate that 25 percent of all the uranium purchased by U.S. electric utility companies come from U.S. uranium mines. Fighting foreign competition would matter more, they say, than repealing environmental protections.

But it still might not be enough to rebound the industry to its previous highs or keep it solvent over the long term.

The international market for uranium has been decidedly less grim — at least, it was up until the 2011 Fukushima nuclear disaster in Japan (and the subsequent closure of power plants there and in Germany). That event sent the price of uranium into a tailspin and left the world with large stockpiles of uranium and little demand for it. Even countries usually seen as the big winners in the global uranium mining industry have scaled back production. There are new nuclear power plants being built in China, India, Russia and other countries, said Keith Florig, who is a research scholar at the University of Florida and studies risk and the nuclear energy industry. But those countries’ power plants are primarily buying uranium from domestic mines or from mines they have developed and control in other countries. Worldwide demand for uranium could go up and still leave U.S. producers behind.

One reason that U.S. companies would have trouble competing with producers from those other countries is the difference in environmental regulations. In 2014, the most recent year for which data is available, around 40 percent of the world’s uranium came from Kazakhstan, a country that, according to experts, can offer its uranium at a very cheap price because it’s not doing much in the way of environmental protection. Kazakhstan mines uranium by pumping a sulfuric acid solution into the ground and processing the uranium that binds to it. In the U.S., this process, called in-situ mining, is less toxic, but more expensive, using a sodium bicarbonate solution. U.S. uranium miners also have to remediate the groundwater at in-situ leaching sites, something that Cash and Goranson said isn’t required in Kazakhstan.

Uranium producers and politicians from uranium-producing states have pushed back against recent EPA efforts to increase groundwater protections at in-situ mining sites, but Cash said the U.S. uranium industry doesn’t want to mine the way that Kazahkstan does. “We want to protect the environment,” he said. “We think we should be good stewards of the environment.” But that lack of environmental protection in Kazhkstan makes a difference on price — $10 per pound according to calculations put together by his engineers. Cash framed the 25 percent purchase mandate that he and Goranson have requested as a way to make up for that price difference between the two countries.

Of course, the catch is that while the Ur-Energy and Energy Fuels plan would help prop up the American uranium industry in the short term, it doesn’t account for the fact that the nuclear power industry here isn’t growing. In fact, it’s contracting. The U.S. Energy Information Administration’s projections for nuclear power demand are even worse than for coal. By 2050, the agency expects the U.S. electric system to use about 20 percent less nuclear power than it did in 2016. Uranium mining companies are asking for a guaranteed slice of an ever-shrinking pie.

In the wake of a mass shooting at a high school in Parkland, Florida, the FiveThirtyEight Politics podcast devotes an entire episode to the debate about guns in America — what the public wants, how the politics of guns have changed and what Washington will do. Jill Lepore, a Harvard professor and staff writer for The New Yorker, joins to discuss how the National Rifle Association has affected views on gun rights since the 1970s.

You can listen to the episode by clicking the “play” button above or by downloading it in iTunes, the ESPN App or your favorite podcast platform. If you are new to podcasts, learn how to listen.

The FiveThirtyEight Politics podcast publishes Monday evenings, with occasional special episodes throughout the week. Help new listeners discover the show by leaving us a rating and review on iTunes. Have a comment, question or suggestion for “good polling vs. bad polling”? Get in touch by email, on Twitter or in the comments.

Graphics by Gus Wezerek

The 2018 Winter Olympics are basically halfway over,Which is sad, because winter is the best kind of Olympics.

‘>¹ and the usual suspects are off to a great start. The Norwegians, the kings of cross-country skiing, currently lead the medal table with 22 pieces of hardware, including seven golds. The Germans, who traditionally rule luge and biathlon, are not far behind with nine golds and 17 medals. The United States, meanwhile, is in a four-way tie for fifth, having nabbed only nine total medals.

How many should we expect the U.S. to have at this stage of the games, though? Since medals in different sports are awarded at different times, it can be difficult to know whether a country is behind where they should be or right on track. To help with that, we created a simple medal tracker. It compares a given country’s medal count with how many we’d expect based on its historical performance in the sports that have already been completed at this year’s games. It also tells you how many remaining medals a country should pick up over the rest of the Olympics if its athletes play to form. (One note on this: We’re looking at the broad categories of events that make up the Olympics — Alpine skiing, snowboarding, curling, etc. — not the specific events within those categories.)

Here’s how it works: We collected Winter Olympics medal data going back to 1998, when snowboarding was added to the official program as a new sport,As of the 2018 Games, snowboarding is the most recent new sport to be added to the Winter Olympics.

‘>² and then calculated the share of medals that each country won in each sport. For example, from 1998 to 2014, the U.S. won 33 percent of all gold medals in snowboarding, to go with 17 percent of silvers and 30 percent of bronzes. (Yes, we’re pretty good at snowboarding.) Then we used those historical rates to set the baseline expectations — the expected medals — for the 2018 Pyeongchang Games.For example, anytime a snowboarding medal is awarded, we add 0.33 golds, 0.17 silvers and 0.30 bronzes to the U.S.’s expected medal tally.

“>³ There is one big exception to note: The Olympic athletes from Russia use the Russian Federation’s expected-medal rates, but with a 25 percent reduction to reflect the reduced number of Russian athletes competing in the 2018 Games (plus whatever other negative effects the Russian doping scandal might have on their medal tally).

Add up all of those expected medals, and you can see where a country “should” be based on what it’s good at and what’s happened at the games so far. And the U.S. is definitely underperforming in South Korea, relative to expectations. Based on the events that have already been completed at the games, we would expect to have seen 18 American podium appearances thus far, which is exactly double the number the U.S. has actually had. From Lindsey Jacobellis’s coming up short again in boardercross to Mikaela Shiffrin’s shocking non-medal in slalom, Lindsey Vonn’s super-G struggles and Nathan Chen’s disappointing fifth-place finish in men’s figure-skating, no country is off to a rougher start in Pyeongchang than the Americans.

The good news for the U.S., however, is that there are plenty of medal events remaining in which American athletes excel. Based on its rates over the 1998-2014 period, we would expect the U.S. to pick up about 18 more medals before the games are over, which is more than any other country’s projection. Even if that happens, however, our tracker projects that the U.S. would finish a distant fourth in the final medal table — which would be its worst showing at the Winter Olympics since 1998 — but at least it would mean the second half of the games was a lot better than the first.

For Norway, this is shaping up to be its best performance at the Winter Games ever. Even though a number of their best events are over, the Norwegians should still finish strong. Indeed, if they (and everyone else) simply perform to expected baselines over the rest of the Olympics, Norway will finish first in the standings, with 34 medals, ahead of Germany and Canada.

One of my least favorite questions is: “Did Russian interference cost Hillary Clinton the 2016 election?” The question is newly relevant because of special counsel Robert Mueller’s indictment of 13 Russians on Friday on charges that they used a variety of shady techniques to discourage people from voting for Clinton and encourage them to vote for Donald Trump. That doesn’t necessarily make it any easier to answer, however. But here are my high-level thoughts in light of the indictment. (For more detail on these, listen to our emergency politics podcast.)

1. Russian interference is hard to measure because it wasn’t a discrete event.

You know what probably did cost Clinton the election? The letter that former FBI Director James Comey sent to Congress on Oct. 28, 2016, and the subsequent media firestorm over it. The impact is relatively easy to measure because it was the biggest news event in the final two weeks of the campaign, and we can compare polls conducted just before the Comey letter to the ones conducted just after it.Even there, there’s some ambiguity — but considering that Clinton essentially lost the election by only 0.8 percentage points (Trump’s margin of victory in the tipping-point state, Wisconsin) and that the Comey letter coincided with a polling shift of about 3 points toward Trump, we can be reasonably confident that it was enough to make the difference.

‘>¹

Russian interference isn’t like that. By contrast, the indictment (and previous reporting on the subject) suggests that the interference campaign had been underway for years (since at least 2014) and gradually evolved from a more general-purpose trolling operation into something that sought to undermine Clinton while promoting Trump (and to a lesser degree, Bernie Sanders). To the extent it mattered, it would have blended into the background and had a cumulative effect over the entirety of the campaign.

2. The magnitude of the interference revealed so far is not trivial but is still fairly modest as compared with the operations of the Clinton and Trump campaigns.

The indictment alleges that an organization called the Internet Research Agency had a monthly budget of approximately $1.25 million toward interference efforts by September 2016 and that it employed “hundreds of individuals for its online operation.” This is a fairly significant magnitude — much larger than the paltry sums that Russian operatives had previously been revealed to spend on Facebook advertising.

Nonetheless, it’s small as compared with the campaigns. The Clinton campaign and Clinton-backing super PACs spent a combined $1.2 billion over the course of the campaign. The Trump campaign and pro-Trump super PACs spent $617 million overall.

In terms of headcounts rather than budgets, the gap isn’t quite so dramatic. The “hundreds” of people working for the Internet Research Agency compare with 4,200 paid Clinton staffersIncluding Democratic National Committee staffers and people who worked for state parties.

“>² and 880 paid Trump staffers.Including Republican National Committee staffers and people who worked for state parties.

“>³ Russian per-capita GDP is estimated at around $10,000 U.S. dollars — about one-sixth of what it is in the U.S. — so a $1.25 million monthly budget potentially goes a lot farther there than it does here. The Russian efforts were on the small side as compared with the massive magnitudes of the campaigns, but not so small that you’d consider them a rounding error.

3. Thematically, the Russian interference tactics were consistent with the reasons Clinton lost.

How did Trump win? Or more to the point, how did Trump win given that he only had a 38 percent favorability rating among people who voted on Election Day? The answer is partly the Electoral College, of course. But it’s also that Clinton was really, really unpopular herself — almost as unpopular as Trump — with a favorability rating of just 43 percent among Election Day voters. Also, the substantial number of voters who disliked both Clinton and Trump went to Trump by a 17-point margin. Voters really weren’t willing to give Clinton the benefit of the doubt.

That’s largely because Clinton was viewed as dishonest and untrustworthy, exactly the sort of message that the Russian campaign (which used hashtags such as #Hillary4Prison) was trying to cultivate. Trump, of course, was trying to cultivate this message too. Media coverage often struck the same themes. And voters sometimes heard variations on this theme from Sanders and his supporters in the more contentious moments of the Democratic primaries. Was some of this Clinton’s fault? Yep, of course. Would Clinton still have been “Crooked Hillary” even without the Russians? Almost certainly. But the Russians were at least adding fuel to the right fire — the one that wound up consuming Clinton’s campaign.

The indictment also alleges that the Russian conspirators sought to suppress African-American turnout. A decline in black turnout was an important — perhaps even decisive — factor in Clinton’s defeat, although it may have been inevitable given that Barack Obama, the first African-American president, had been on the ballot in 2012.

Overall, then, my view on the effects of Russian interference is fairly agnostic. I tend to focus more on factors — such as Clinton’s email scandal or the Comey letter (and the media’s handling of those stories) — that had easier-to-prove effects. The hacked emails from the Clinton campaign and the DNC (which may or may not have had anything to do with the Russians) potentially also were more influential than the Russian efforts detailed in Friday’s indictments. Clinton’s Electoral College strategy didn’t have as much of an effect as some people assume — but it was pretty stupid all the same and is certainly worth mentioning.

But if it’s hard to prove anything about Russian interference, it’s equally hard to disprove anything: The interference campaign could easily have had chronic, insidious effects that could be mistaken for background noise but which in the aggregate were enough to swing the election by 0.8 percentage points toward Trump — not a high hurdle to clear because 0.8 points isn’t much at all.

Perhaps there are more clever methodologies that one could undertake. For instance, if we knew which states the efforts were concentrated in, we might be able to make a few additional inferences. Maybe some of that information will come to light as the result of Mueller’s probe and further investigative reporting. For the time being, however, we’re still somewhat in the dark.

On any given week during peak soccer season, FiveThirtyEight offers projections for dozens of club soccer matches across the globe. The sheer volume of matches taking place this time of year can be paralyzing. With that in mind, we’ve added a feature to our club soccer predictions that rates upcoming matches on their quality and importance. You can use this page to pick a few good ones to be sure not to miss.

This week’s biggest match — rated an overall 96 out of 100 — is today’s Champions League round of 16 first leg between Real Madrid and Paris Saint-Germain. This is a bit of a no-brainer — it features Neymar and Cristiano Ronaldo leading the second- and third-best teams in the world against each other in a high-stakes clash. But there are some other good matches to watch: Borussia Dortmund and Atalanta — two of the best eight remaining teams in the Europa League — play each other on Thursday in the round of 32. If we dig deeper, Empoli and Parma — two teams fighting for promotion and the league title at the top of a very tight Italian Serie B — play each other Saturday. And Manchester United plays Chelsea on Feb. 25 in the Premier League in what is a pivotal match for Champions League qualification.

Here’s how we calculate our match ratings:

Quality is simply a measure of how good the teams are. Specifically, it’s the harmonic mean of the two teams’ Soccer Power Index ratings. (We’re using the harmonic mean instead of merely averaging the two ratings because in lopsided matches it limits the impact of very high or low ratings, resulting in a more balanced number.) Because every team has an SPI rating between 0 and 100, our match quality stat also ranges from 0 to 100.

Importance is a measure of how much the outcome of the match will affect our forecast for how likely the two teams are to win the league, or be relegated or promoted, among other things. To calculate it, we generate probabilities conditional on each team winning the match and then find the difference between those two possible numbers.

We consider different factors depending on which league the match is being played in. For some leagues, our forecasts cover winning the league and qualifying for the Champions League, for example.

We take a weighted average of the change in each applicable factor and scale the result to between 0 and 100. All leagues are treated equally when calculating importance, so a match to decide the winner of the Swedish Allsvenskan would rate just as high as a match to decide the winner of the English Premier League.

The overall match rating is just the average of quality and importance.

Visit our club soccer predictions to explore the ratings of all the upcoming matches yourself.