The values assigned to serious burn injuries and loss of life were based on values calculated by NHTSA in 1972.[81] In the memo Ford estimated the cost of fuel system modifications to reduce fire risks in rollover events to be $11 per car across 12.5 million cars and light trucks (all manufacturers), for a total of $137 million. The design changes were estimated to save 180 burn deaths and 180 serious injuries per year, a benefit to society of $49.5 million.