Sometimes when you do research on one thing, you find something interesting about a related topic. Back in March, I was contacted by Sports Illustratedís Alexander Wolff regarding a piece he was working on for the SI tournament preview. (When the owner of the Vermont Frost Heaves calls, you get to work.) One of the things that Wolff mentioned was that the NCAA had said that 67 percent of points scored by the winning team in the final minute were on free throws. I was skeptical that the NCAA could put together accurate figures on anything, so I had to run the numbers myself. Sure enough, the NCAA knew their stuff. I shall never doubt them again.
But that was the tip of the iceberg in terms of shooting stats that can be mined from play-by-play data. Why just look at the last minute and not all minutes in a game? Surely some other nuggets could come from such a pursuit. It turned out that there were a few interesting discoveries worth sharing.
The thing that jumped out at me was that the first two to three minutes of a typical game are action-starved. And it looks like the blame can be put on offenses being too passive. Letís start with a graph showing the percentage of points that come from each shot type based on time remaining in regulation.
There are three lines here, but the free throw rate seems to control the other two values. (The ratio of two-point baskets to three-point baskets doesnít change much during the game, although there is a slight decrease in the second half compared to the first.) Points scored on free throws gradually increase in each half, owing mostly to the increasing likelihood of the bonus coming into effect. But there are some peculiarities in the data if you look closer.
The minute with the lowest percentage of points scored (7.6) at the free throw line is the first minute of the game. This shouldnít be too surprising--if you didnít just read this and had to noodle through which minute contained the fewest free throws, I think youíd eventually come to the correct answer with a little thought. Nobody likes to pick up a foul early in the game, so one can understand that the defense might avoid contact when challenged early.
No doubt that's a contributing factor, but thereís a lot more to it than that. Further examination reveals that the offense is actually at its most passive at the beginning of the game. Scorekeepers all across the nation categorize two-point shots as either jumpers or something else implying a shot near the rim (lay-up, dunk, or tip).
In the first minute of the game, 1.51 jumpers are taken for every close two-point shot, easily the highest rate of any minute in the game. The second minute of the game has the second-highest with a ratio of 1.39. Compare that to the first minute of the second half, where there are just 1.24 jumpers for every close shot. In addition, dunks comprise just 3.7 and 4.0 percent of all shots in the first and second minutes of the game, respectively, lower than at any other time. Thereís just not much going on near the rim early in the game. In other words the reason there are fewer foul shots in the opening minutes is because offenses are less aggressive, not because defenses are avoiding contact.
There's one other notable trait to be found in the first minute of each half. Because the half starts with a half-court possession (except for the odd transition off the jump ball), there are necessarily fewer transition opportunities, a characteristic that tends to skew the number of close shots downward.
In spite of the fact that this effect should disappear by the second minute, however, it does not. Itís also noteworthy that free throw attempts increase by 22 percent from the second minute to the third minute, a time where the bonus is very rarely a consideration. This is compelling evidence that thereís an offensive conservatism to be found in the first few possessions of the game. And on balance, this hurts the offense.
While Iím here, allow me to dump some more data on the table. Letís look at how shooting percentages evolve during the game.
The two worst minutes for effective FG percentage are the final minute of each half, owing to the influence of buzzer-beating attempts more than anything else. The next worst minute is the first one of the game, where teams shoot a 47.8 eFG percentage. Part of this is attributable to the lack of transition chances, but this figure is much lower than the 50.3 that we find in the first minute after halftime, where the same limitation exists.
While the chart may look like a bunch of random wiggly lines, thereís more insight if one looks closely. In general, shooting percentages on two-pointers are higher across the board in the second half when comparing similar minutes in the first half. The improvement in two-point accuracy is almost entirely explained by the increase in the number of close shots. Three-point percentage doesnít really change by half and you can see the effect of desperate offenses firing contested threes as time remaining gets scarce in the second half.
Should teams be taking more threes early in the game? Or being more aggressive with their early twos? I donít know, but thereís an imbalance there. Maybe teams should start that energy guy that normally comes off the bench at the 12 minute mark to spice things up. Regardless, if you find yourself running a bit late for the big game, you probably wonít miss much if you donít catch the first couple of minutes.
Ken Pomeroy is an author of Basketball Prospectus.
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