The 2016 NFL season is now in the rearview mirror, ending with a Super Bowl that will be talked about for years to come. Most of the records in the Big Game were set by winning Patriots quarterback Tom Brady, leaving Falcons quarterback Matt Ryan with plenty to despair. The day before the Super Bowl, however, Ryan had something to celebrate: he was named the league’s MVP.
Ranker has a popular list for Players Most Likely to Be the 2016-17 MVP. The list was published in November 2016, and over 20 players received a total of more than 30,000 thumbs-up and thumbs-down votes. We were interested in whether this list predicted Ryan’s win, and how the patterns of opinions expressed by the voters changed over time.
The figure above summarizes the raw voting data for Matt Ryan. The black cross markers show the empirical proportion of up-votes to total votes on each individual day that votes were cast. The size of the crosses corresponds to how many votes were cast on that day. There is an increase in the proportion of up-votes, beginning around January 15. The two Sundays, marked on the x-axis, which includes the NFC Divisional Round and NFC Championship, on January 15 and 22. Ryan and his teammates played their best games of the year as the franchise made its second Super Bowl appearance.
The blue line in the figure above shows the cumulative proportion of up-votes to total votes over each day voting was active. This cumulative proportion increases after January 15, but not to a large degree, because of the accumulated earlier votes continuing to affect the overall proportion. The problem with this analysis is that it assumes voting always reflects the same opinion, so that all votes are lumped together, and the thumbs-up or thumbs-down votes last November count equally with votes registering an opinion right before the MVP was announced.
So, we developed a new model to analyze these data, as an alternative to cumulative opinion. Our new model tries to measure current opinion, rather than cumulative opinion. It does this by allowing for swings in opinion. For something as hotly contested like NFL MVP, it’s easy to imagine opinions changing based on a good or bad game, or even an injury. Between change points, our model assumes the crowd has a stable opinion, but each time a change point is encountered, the opinion can shift. Our algorithm for applying the current opinion model is able to identify how many changes are evident in a sequence of voting data, where those change points are, and what the stable opinion in each stage are.
The results of applying the current opinion model to Matt Ryan’s data are shown in the figure above by the red line. Two change points are inferred, around November 22, 2016 and January 22, 2017. Opinion starts just below 60%, drops to about 30%, and then rises again to a final value just above 60% in time leading into the award’s announcement.
The two panels in the figure above shows the cumulative opinion (left-hand panel) and current opinion (right-hand panel) measures for eight leading candidates for the MVP award, including Ryan. These players were all heavily voted on, and include the leading candidates discussed in the media. For both opinion measures, the natural way to make a prediction is to order the players according the opinion right before the February 4 announcement. Cumulative opinion ranks Ryan in fifth place, behind Ezekiel Elliott, Dak Prescott, Tom Brady, and Aaron Rodgers. Rookie stars Elliott and Prescott had dominant seasons for the Dallas Cowboys, but the early MVP excitement faded to a more realistic assessment that rookie winners are less likely, nevertheless teammates. Their prospects of winning were faded once the Cowboys lost in their playoff game. Brady and Rodgers, contrarily, are well-established and high-profile perennial favorites for the MVP award.
The current opinion measure shows that Ranker voters had it right, correctly predicting Matt Ryan as the winner. It is interesting to see that Brady ranked second according to current opinion, since he was widely tipped as the only other serious possible winner in the days before the award was announced. Both Elliott and Prescott show plausible and interpretable downward changes in opinion over the period of voting. Rodgers shows an interesting large, but short-lived drop in opinion immediately after Green Bay was eliminated on January 22. Generally, many of the inferred change points occur immediately following a significant game result, although there is no constraint in our analysis that requires this. In effect, the change points reveal that game-day performance is the most likely thing to sway opinion.
The overall message is that voting data on Ranker expresses valuable crowd opinions, especially when analyzed in the right way, by allowing for opinion to change. When making predictions about an upcoming event, more recent opinion will often be better. More information is available, and less time must pass before the answer is known, reducing uncertainty. Whether or not it makes Matt Ryan feel better, our analysis shows that Ranker voters are on board with him being the NFL’s Most Valuable Player.
– Michael Lee and Lucy Wu