"What we found is boosters are doing a much better job than they did just a few years ago," says Ann McCartt.
In 2008 the institute could only find ten booster seats worthy of its "Best Bet" rating.
Today there are nearly 50, including 12 models introduced this year like the Graco Turbobooster and the Harmony Highback.
The institute says these and others allow the lap belt to fit tightly over the thighs.
"It's not riding up on the tummy, which is prone to injury in a crash. And the shoulder belt is fitting snuggly across the center of the shoulder," McCartt explains. It's not riding off to the side, it's not riding up on the neck."
Manufacturer Dorel Juvenile Group has five of its booster seats on the institute's "Best Bet" list.
Still, two others, the Safety 1St All-In-One and Alpha Omega Elite, were the only two "Not Recommended".
The institute says they leave the lap belt too high on the abdomen and the shoulder belt too far out on the shoulder.
In a statement, Dorel said it stands behind all of its seats that have been proven to protect children in real-world situations and real-world crashes.
Boosters are generally intended for 4 to 8 year olds who weigh up to 80 pounds.
A detailed list of booster seats tested by the Insurance Institute can be found at www.iihs.org.
For more detailed information about child safety seats, including where you can get a free fitting, visit: carseatscolorado.com.
(Copyright © 2012 NBC Universal, All Rights Reserved)