FIGURE 2-4 American Bar Association membership: Intellectual Property Law Section and total. SOURCE: American Bar Association.

(Scherer et al., 1959; Taylor and Silbertson, 1973; Mansfield, 1986; Levin et al., 1987; and Cohen et al., 2000). But among R&D executives of large firms there has been a modest increase in the importance attached to patents between the so-called Yale survey conducted in 1983 by Levin and colleagues and the 1994 Carnegie-Mellon survey (CMS) conducted by Cohen and colleagues. For the protection of product innovation, patents were ranked first or second in 7 of the 33 industries in the Yale survey and in 12 industries in the CMS survey (Cohen, 2000).

This is consistent with other indirect evidence that patents have come to occupy a more central role in corporate decision making. Allison and Lemley (2002) compared a random sample of 1,000 patents issued between 1996 and 1998 with a similar random sample issued 20 years earlier (1976-1978) to determine how the patent system changed over time. Two dramatic changes emerged from the data. First, obtaining a patent has become a more complex process, involving more claims, citing more prior art, taking longer, and involving more refilings. Second, patents today are much more heterogeneous than their counterparts two decades ago. Allison and Lemley suspect that changes in technology and prior art search methods (for example, automated searches of scientific and technical literature) account in part for the changes, but the increased salience of