My question though is whether it affected the public's perception of the expected margin of victory at the end of games, i.e. the gambling spread. Historically, spreads around a multiple of 7 or 3 are very sticky (toggle numbers around these multiples in SBR's half-point calculator and see the difference). In other words, once a spread is around, say, -7, moving to -6.5 or -7.5 is a much bigger jump (percentage-wise) than -5 moving to -4.5 or -5.5. It is much more likely a score finishes at exactly -7, which would greatly increase the chances of one side covering in this example at -6.5 or -7.5.
So did spreads move off of these multiples of 3 or 7 as the season progressed and the public (theoretically) adapted to the lower accuracy on extra point (XP) attempts? I first looked at the closing lines from last season that were on multiples of 7 only throughout the regular season. If XP accuracy decreasing had an effect, we would expect the frequency of spreads to decline throughout the season:
Likewise, we would expect the number of spreads within a half-point of 7 to increase throughout the season:
Neither frequency shows much of a linear trend from the beginning to the end of the season. So I expanded to multiples of both 3 and 7:
