Figure 3.1-1: Annual Number of EV-related United States Patents Granted from 1980 to 1999.
During the years of low and declining patent activity related to EVs (1980 to 1991), all patent activity in general is increasing. In fact, all patent activity increased slowly and steadily throughout the period from 1980 to 1998, such that by 1998 the number of patents had increased by a factor of 2.3. In the time period 1991 to 1996, the rate of patent activity related to EVs increases faster than all patent activity. By 1991, EV-related patent activity had dropped to only 0.14 times that in 1980; by 1998, over 6 times as many EV-related patents were granted every year as had been in 1980.
These observations suggest, and statistical analyses of these data confirm, that increases in the number of EV related patents are not correlated with increases in overall patent activity. (Details of the statistical analysis are contained in Appendix 1.) We are therefore more inclined to attribute the upturn in EV-related patent activity to the fact that after 1990 all automobile manufacturers had to develop EV technology to meet the ZEV Program.
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