One of the main problems in assessing the relative efficiency of multi
ple retail outlets is the fact that customers are an essential compone
nt of the ''production process'' in retailing. Hence, the efficiency o
f a particular retail store depends both on the seller's and the buyer
s' efficiency. While there is often data an each store's inputs to the
production of retail services, the contribution of each store's custo
mers to this process is difficult to measure, and often goes unmeasure
d. In the absence of data on variation in customer efficiency across s
tores, it is difficult to make comparisons of the relative efficiency
of the retailer's operation across stores In this paper, we propose to
solve the problem of missing data on customer inputs by treating stov
es as members of different latent classes, where the classes are defin
ed by differences in customer inputs and other market characteristics.
We consider the clusterwise estimation of multiple translog cost func
tions, which identifies sets of retail outlets operating under similar
conditions and simultaneously estimates multiple cost functions for t
hese classes. The efficiency of each outlet would then be evaluated re
lative to others in its class, which allows for a more equitable evalu
ation of each retail outlet, in comparison to other units operating un
der similar conditions. We apply this approach in the evaluation of mu
ltiple branches from a commercial bank in Latin America, and compare t
he efficiency measures obtained from it with measures obtained from ot
her methods, using the bank's central managers' classification of mark
ets as a benchmark. Our results indicate that the clusterwise estimati
on of translog cost functions leads to a more equitable assessment of
the branches more in tune with the market differences perceived by the
bank managers.