Grist points to a study where students put a rubber turtle on the highway and noted that out of 257 cars that passed, seven went out of their way to hit the turtle. That's 2.7237%. Sarah Miller titled their post People will go out of their way to hit turtles with cars, because people are jerks.
That rang a bell; TreeHugger wrote about a Canadian study in 2007, titled Study Proves 2.7% of Drivers Are Stupid Jerks.
They alternated between placing a plastic turtle, a rubber snake, a white cup and a grease control line on the centre of the road. The grease line helped researchers know how many drivers passed over the centre line by mistake. They hid in the bushes and watched 1900 cars, and found that 2.7% of drivers swerved onto the centre line specifically to run over the reptiles.
Fascinating that two separate studies in two different countries come up with the identical percentage. Take take a lethal weapon that is regulated similarly in both countries, like cars, and the turtle murder rate is identical. Take guns, and the American people murder rate is 8.1 times the Canadian rate. There's a lesson here.