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effects of mergers and acquisitions (M&As) on subscriber bases, all subscribers obtained
through M&As were excluded. We also controlled the total number of acquired firms whose
main business area is classified as 4812 according to the Standard Industrial Classification
Code.
Intra-industry ties of TMT.
Two types of manager intra-industry ties were examined:
ties to the CTIA and ties to other cell-phone service operators. TMT’s ties to the CTIA
represent the number of top managers who had been a member of the CTIA directorial board
prior to the focal year. TMT’s ties to other firms represent the number of industry firms at
which each manager had worked as a top manager (vice president or higher).
Extra-industry ties of TMT.
TMT’s extra-industry ties represent the number of firms at
which each manager had worked as a top manager (vice president or higher) in firms outside
the cell-phone service industry.
Industry age.
The industry age variable is measured by the number of years since the
beginning of the cell-phone service industry in 1983.
Intra-industry experience addition of TMTs.
The variable for the intra-industry
experience addition of TMTs is measured by the increase in the average years that TMT
members had worked in the mobile communications service industry as top managers from
year
t
-1 to
t
.
Control variables.
To control for the increase in firm subscribers because of the growth
of the entire industry,
industry growth at t
was included. This variable measures the growth
rate of cell-phone subscribers at the industry level in year
t
. To control for the impact of
competition on firm performance, the four-firm concentration ratio in the industry,
CR4
, is
used. To control for the increase in firm subscribers because of technological advancement, a
dummy variable specifying the time period before a shift to digital technology—
predigital
regime
, is used. Regarding time-invariant firm effects, the number of acquisitions that the
focal firm completed in the focal year,
N of acquisitions at t
, is used to control for the
increase in firm subscribers from acquisitions. In addition,
firm size at t
-1, which measures
the number of subscribers of the focal firm at year
t
-1, and
Below Industry Median Firm
Size
, which is a dummy variable specifying whether firm size is below the industry median
at
t
-1, are included, according to the firm growth literature (Geroski, 2002). The number of
managers in the TMT,
Size of TMT
, is included to control for the amount of human capital in
the TMT (Hambrick and Mason, 1984). To control for potential systematic errors caused by
missing executive background information, the number of top managers with missing
information, #
Execs w/ missing info
, is included. Firm-level variables such as entry date and