[SD987]

Because they're expensive and not sold in great number...from the NHTSA FAQs:

"Every year the agency chooses those new vehicles which are predicted to have high sales volume, those which have been redesigned with structural changes, or those with improved safety equipment. This allows us to provide star rating results that best represent what is actually being purchased in the marketplace. These vehicles are purchased from dealerships from across the country, just as you the consumer would. The vehicles are not supplied directly to NHTSA by the manufacturer – a common misperception.

Since NHTSA selects vehicles for rating based primarily upon sales volume, not all vehicles can be rated. Those with smaller sales volume may not have been selected. Even though a vehicle may not have been rated under the New Car Assessment Program, all vehicles sold in the U.S. are certified by the manufacturer as complying with all applicable Federal motor vehicle safety standards."

Euroncap rated roadsters and they all came out pretty much the same. I think it would be safe to extrapolate these results to get a picture on the Box...

http://www.euroncap.com/content/safety_ratings/ratings.php?id1=8

This site purports to have data, but I'd have to question....from where?

http://www.crashtest.com/porsche/ie.htm