The number of vehicles in Kerala has risen drastically in the last 12 years, and the immediate fallout of this has been an increase in respiratory diseases. Motor vehicles in the state grew from 581,000 in 1990 to an astonishing 2.31 million in 2002, while vehicles per 100 sq km grew from 1,495 to 5,958 in the same period, according to the latest economic review of the Kerala government. Kerala's commercial capital Kochi leads in vehicle population at 406,000 followed by Thiruvananthapuram with 320,000 and Thrissur with 241,000 vehicles. The hilly districts of Idukki and Wayanad have the least vehicular population with 36,000 and 32,000 vehicles respectively.