  Technology is a complex system, with technologies relating to each other in a
space that can be mapped as a network. The technology network's structure can
reveal properties of technologies and of human behavior, if it can be mapped
accurately. Technology networks have been made from patent data, using several
measures of proximity. These measures, however, are influenced by factors of
the patenting system that do not reflect technologies or their proximity. We
introduce a method to precisely normalize out multiple impinging factors in
patent data and extract the true signal of technological proximity, by
comparing the empirical proximity measures with what they would be in random
situations that remove the impinging factors. With this method, we created
technology networks, using data from 3.9 million patents. After normalization,
different measures of proximity became more correlated with each other,
approaching a single dimension of technological proximity. The normalized
technology networks were sparse, with few pairs of technology domains being
significantly related. The normalized network corresponded with human behavior:
we analyzed the patenting histories of 2.8 million inventors and found they
were more likely to invent in two different technology domains if the pair was
closely related in the technology network. We also analyzed 250 thousand firms'
patents and found that, in contrast, firms' inventive activities were only
modestly associated with the technology network; firms' portfolios combined
pairs of technology domains about twice as often as inventors. These results
suggest that controlling for impinging factors provides meaningful measures of
technological proximity for patent-based mapping of the technology space, and
that this map can be used to aid in technology innovation planning and
management.
