A study of Patent Thickets (1.31Mb) - UK Intellectual Property Office

A Study of Patent Thickets 73
Table 7.1 above presents the Z-scores for this measure. 38 While there is a broad range in these
values they are always so high that we can be sure that triples arise far more frequently in all of
these data sets than we would expect if the triples just arose randomly.
Following Milo et al. (2004b) we summarize our findings using significance profiles for each of
these areas. A significance profile is the vector of Z scores normalized to length 1. This
normalization allows us to view the relative importance of the Z-scores for different motifs
abstracting from their absolute values which are affected by the number of observations in the
six different data-sets we analyze.
Figure 15 below presents the six triad significance profiles based on the Z-scores we extracted
from our data using FANMOD for each of the three technology areas in each of . The figure
contains 9 of the 13 network motifs presented by Milo et al. (2004b). The remainder did not
arise in our data or were not significant. A comparison with the significance profiles presented
in Figure 1 of their paper for the World Wide Web and social networks reveals that the shape of
our significance profiles for the network motifs 7-13 is quite similar. There are clear peaks for the
motifs 9, 10 and 13 and similarly minima and 8 and 11. It is noticeable that in Telecommunications
and Optics where patent thickets are present there is a significant minimum for the network
motif 12 while this is not the case for the networks analyzed by Milo et al. (2004b). Network
motif 12 is one in which one firm has mutually limiting patents with both other firms, whilst only
one of these two is limiting the other. The fact that this motif is not present with significant
frequency might be evidence for strategic patenting by firms caught in patent thickets. More
study on this point is required before we may be sure however.
Triad Significance Profiles for Selected Technology Areas and Years
38 A measure of statistical significance indicating how many standard deviations the real triples count is higher than
that of the mean of the simulated random samples.