By Brian Burke
Over the past five seasons, attempts from that distance are successful 91.5% of the time. That should put a bit of excitement and drama into XPs, especially late in close games, which is what the NFL wants. But it might also have another effect on the game.
Currently, two-point conversions are successful at just about half that rate, somewhere north of 45%. The actual rate is somewhat nebulous, because of how fakes and aborted kick attempts into two-point attempts are counted.
It's likely the NFL chose the 15-yd line for a reason. The success rates for kicks from that distance are approximately twice the success rate for a 2-point attempt, making the entire extra point process "risk-neutral." In other words, going for two gives teams have half the chance at twice the points.
But it might not be so simple. Teams tend to pass too often on 2-pt conversions, and simply by running more often, the overall success rate could climb to near 50%. That would make the long-run expected value of a 2-point attempt higher than an XP kick attempt. In theory, the strategy options would flip roles. Two-point conversions would become the norm, and XPs would be reserved for late-game tactics when one point is all that's needed to win.
And even if the average 2-point success rate doesn't climb much above 45%, the rates for above average offenses are already above the break-even rate. The same is true for attempts versus below average defenses.
The net advantage of making 2-point attempts the default would be very small, only a fraction of a point per game, so either way, it's not going to make much difference. But that's not any different than how things are now. The net advantage of nearly always kicking the XP rather than usually going for two is tiny.
It's unlikely that the premium would be large enough to compel coaches to abandon convention, even for the best offenses. When two risky options are considered, it's usually the low variance option that's preferred. And in this case, that will always be the XP.