Machlup [19] observed that after patents had withstood the hot debates of the 1860s and 1870s in Britain and Germany economists mostly turned to other topics. In the 20th century, Plant [26] and Arrow [2] were outspoken critics of the patent system as such but even well-known defenders such as Schmookler [31] or Nordhaus have been at best lukewarm: ''The existence of a patent system reduces the uncertainty that inevitably surrounds inventive activity. Without a patent system there is not only technological uncertainty, but also uncertainity about whether the firm can appropriate and license the invention. A patent system is alleged to reduce the second kind of uncertainity, and to the extent that inventors are risk averse, this will increase the level of inventive activity. There is however, an additional uncertainity created by the patent system, namely, whether the firm will be the first to arrive at the Patent Office with the invention. It is not clear which of these influences is more important.'' [22, p. 89].
Empirical studies also tend to show that the influence of the patent system on company inventiveness is weak: ''Taken together, the empirical evidence suggests that firm responsiveness to even significant changes in patent design is limited''. [30], ''According to detailed data obtained from a random sample of 100 firms from 12 manufacturing industries, patent protection was judged to be essential for the development or introduction of one-third or more of the inventions during 1981-83 in only 2 industries pharmaceuticals and chemicals. On the other hand, in 7 industries (electrical equipment, office equipment, motor vehicles, instruments, primary metals, rubber, and textiles), patent protection was estimated to be essential for the development and introduction of less than 10 percent of their inventions. Indeed, in office equipment, motor vehicles, rubber, and textiles, the firms were unanimous in reporting that patent protection was not essential for the development or introduction of any of their inventions during this period.'' [20] or outright harmful ''our preliminary evidence suggests that the pro-patent shift in the 1980s has altered the patent strategies of semiconductor firms, but in ways that go beyond the classic incentives provided of the patent system. On the one hand, stronger patent rights may have facilitated specialization in the industry and may well have supported a market for know-how exchange involving entrant firms. On the other hand, such positive effects are countered by a socially inefficient process whereby firms amass vast patent portfolios simply as bargaining chips.'' [12]
One should be aware that studies on the economics of IP tend to focus on producers (which do have accounting departments), not consumers (which usually do not have accounting departments). A notable exception from this are studies on the economics of libraries that a dependent on the monopoly of journal publishers [32].