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.