Geography Reference
In-Depth Information
survey necessary because there are no secondary data available on alliance behaviour in
the stock photography market. The survey method, however, limits the study of evolu-
tionary processes in at least three ways: it cannot deliver long-term historical data; it will
normally produce incomplete responses; and it produces a survival bias by missing out
those i rms and earlier alliances that were abandoned in the past. The network thus rep-
resents a growth path of surviving i rms rather than the entire network evolution.
Variables
The questionnaire consisted of two parts. The i rst part collected attribute information
on the individual picture agencies such as i rm age, product specialization, i rm size by
number of employees, by image stock and by number of represented photographers
as well as international sales and membership in the national business association.
These attribute items were used to develop relational values of i rm- to- i rm similarity
(homophily) and geographical propinquity between all pairs of agencies (see Table 14.1
for variable dei nitions). The calculation of relational similarities is based on measures
of pair-wise dif erences or coincidence in the individual scores on an item. For each vari-
able, the similarity values are then represented in a similarity matrix for all pairs of
n
×
Table 14
.
1
Variable labels and dei nitions, dyad level
Label
Description
Dependent variable
Sales alliances
Sales alliances between all pairs of agencies for each year, 1989-2005
Independent variables
A
.
Homophily
Firm age
Dif erence in years of foundation in Germany
Digital entry
Dif erence in years of launching an online picture archive
Size employment
Dif erence in number of employees
Size images
Dif erence in size of picture archive
Size photographers
Dif erence in number of photographers (suppliers)
Universality
Dummy, match for two i rms as specialized (= 0) or universal agencies
(= 1)
Specialization
Dummy, match for two i rms according to the kind of specialization of
picture portfolio
International sales
Dif erence in percentage of foreign annual sales
Lobby association
Dummy, match for two i rms according to their membership in the
national industry association BVPA
B
.
Geography
Location
Dummy, match for two i rms according to their location in the same
metropolitan region
C
.
Popularity bias
Indegree centrality
Dif erence in in-degree
Outdegree centrality
Dif erence in out-degree
D
.
Multiconnectivity
Point connectivity
Number of dif erent i rms through which a pair of i rms is connected
Geodesic count
Number of shortest paths between two agencies
