In the period 1987-2007,  Private car population increased more fast than the total car polution, which meant that car began to enter into residents' life, along with the tide of reformation and openning.

1988,1993,1994 were the peaks of private car increasing, and 1990,1996 were two troughs for private car increasing.

the growth rate of private car population waved more strongly than that of total car population. the sales of private car were influenced by the economy policy and environment .