Geography Reference
In-Depth Information
whereas inventors L and M belong to a dif erent component. A pair of inventors
belonging to two distinct components have distance equal to ini nity (i.e. there is no
path connecting them).
3. By
cross- i rm
inventor we mean any inventor whose name has been reported in
patent documents assigned to dif erent organizations. This kind of inventor plays
a fundamental role in connecting teams of inventors belonging to dif erent organi-
zations. For example, in Figure 16.1, inventor F worked for both company a and
company b, thus connecting the team of inventors (B,D ) with the team of inventors
(H,I). Similarly, inventor G worked both for company a and g, thus connecting the
team (B,D,F) with the team (I,J,K).
Using these dei nitions, we may now turn to illustrate how the existence of a linkage
between patents can be ascertained. Three possible relations exist between any pair of
patents from dif erent i rms:
1.
The two patents exhibit
no social connection
, such as when the inventors behind them
belong to socially disconnected components.
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2.
The two patents are linked by a
social connection
, such as when their inventors
belong to the same social component. We can calculate the social distance
between
patents
as the
minimum
geodesic distance between the two closest individuals from
the two teams of inventors (geodesic distance).
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As such, the social distance between
two socially connected patents may vary from 1 to any positive discrete value.
3.
The two patents are linked by a
personal connection
, such as when at least one inven-
tor belongs to both patents' teams. The social distance between two personally con-
nected patents is zero.
8
A limitation of this approach relates to the absence of rules to establish the
decay
of social
links. In fact, we know for sure when two inventors come into contact, namely when they
work together on the same patent for the i rst time. But we cannot be sure they keep in
touch (and exchange information) after that common experience, unless we i nd them
working on more joint patents in the following years. Some contacts established through
co-inventorship may be dropped by one or both parts, but we do not know which ones.
We have addressed this problem by setting a i ve-year maximum life span for all social
ties: the tie binding two inventors who worked on the same patent at time
t
is cancelled
at time
t +
5, and the network is re-calculated accordingly, unless the same inventors are
found to work again together at a time between
t
and
t +
5. This means that for every
year we calculate a dif erent social network.
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Data
To implement the methodology just described, we rely on a biographical dataset of 63188
US inventors and their 66349 patent applications at the European Patent Oi ce (EPO),
i led between 1978 and 2002, in the following i elds: Organic Chemistry, Pharmaceuticals,
and Biotechnology (Table 16.1).
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The choice of the three technical i elds is explained by the high degree of inter-relation
among them. In a previous paper we show how it is often the case that patents whose
main technological class falls in one i eld have secondary classes in one or both of the
