I'd be interested in seeing a good summary in laymen's terms as well. I hope someone has one. I have a couple of links bookmarked on my computer that might help for now.
This article by Marilyn Bull and Dennis Durbin summarizes the study in a way that's a little easier to understand than the abstract, I think. The full study is
here. Table 3 is a good spot to see all the numbers.
The Bull/Durbin articles notes that "Although the study could not provide data dividing the ages by individual months, it is notable that rear-facing car safety seats were more effective than forward-facing car safety seats for both infants under 1 year and children aged 12 to 23 months. The odds of severe injury for forward-facing infants under 12 months of age were 1.79 times higher than for rear-facing infants; for children 12 to 23 months old, the odds were 5.32 times higher."
That "5.32 times higher" figure for the 12-23 month olds is often reworded to be 500% (because it sound more impressive, I believe). That 5.32 times figure is referring to all crash types.
There's also another statistic (which is referring to the entire population of the study, 0-23 months): forward-facing children are 5.53 times more likely to be injured in a side-impact crash. I've seen that number mentioned occasionally as well.
