We also conducted an analysis of returns to scale
among the Indian commercial banks. We characterize
returns to scale with the sign of the intercept of
the supporting hyperplane in the DEA multiplier
problem dual to (2). The intercept of the supporting
hyperplane is not unique for frontier banks, however,
since they are located at the intersection of two or
more supporting hyperplanes. In general, banks exhibit
increasing, constant or decreasing returns to
scale at their optimal radial projection according as
the maximum intercept of their supporting hyperplane
is negative, the minimum and maximum intercepts
bound zero, or the minimum intercept is positive,
respectively; see Banker and Thrall (1992). Our
analysis shows that most banks displayed decreasing
returns to scale. Indeed every Indian bank in every
year in the sample period operated in the decreasing
returns to scale region of production technology. The
persistence of diseconomies of scale could possibly
result from the RBI's branching policy. Indian banks
are required to open branches under the branching
policy, but are not allowed to close unprofitable
branches. This policy prevents optimizing resources
across the branch network because banks have neither
control over the location of branches nor the
ability to close loss-making branches. In sharp contrast,
foreign banks exhibited increasing and constant
as well as decreasing returns to scale. Foreign banks
tend to have smaller branch networks, since they
have not yet fully expanded their business and have
not been forced by regulators to expand branch
networks beyond their optimal size.