Electronic stability control has been mandated by the NHTSA since 2012 (they required at least 55% of 2009 models sold to be equipped with it, 75% of 2010 models, and 95% of 2011 models)

Also in 2007 about half of all new cars sold were equipped with it.

The NHTSA and the Insurance Institute for Highway safety estimate that stability control could prevent 1/3 of fatal accidents.

If a substantial portion of cars started to be equipped with it around 2005 (they did), it's a likely explanation for a decline in traffic fatalities since then.

> Electronic stability control has been mandated by the NHTSA since 2012 (they required at least 55% of 2009 models sold to be equipped with it, 75% of 2010 models, and 95% of 2011 models)

I should have looked that up before stating the opposite. My mistake.

> Also in 2007 about half of all new cars sold were equipped with it.

I've read that the average vehicle age is about 10 years. That means that only now are we getting to the point where the vast majority of vehicles would be equipped with electronic stability control. Looking at the FARS page I cited earlier, the decline in fatality rate is pretty clear, but how prevalent ESP was and how much it changed in that time period is not as clear (at least I don't have the data for it).

Some very back of the envelope math shows that each year about 7% of vehicles are replaced each year, so by 2012 we can estimate that about 35% of cars would have been 2007 models or newer.

So by 2012 we have a minimum of 17% of cars with electronic stability control (probably much higher given that by 2010 75% of cars sold were mandated to include it). If cars with electronic stability control are really involved in 1/3 few accidents, then we'd expect a very sizeable decrease in vehicle fatalities due to electronic stability control alone by 2012 and probably much earlier.