profits made by the carriers were dependent on the capital the carriers had during these periods.
Results also reveal that categorizing the carriers into commodity groups and regions had no
significant impact on the profits of the firms during the study.
Table 2 shows the results for the pooled estimates for the period 1994-2002. The results
reveal the profits derived by the pooled firms were highly dependent on the market share
variable (MKS) and the cash and equivalent variable (CAE) during the study. Similar to the
annual estimates, the profits derived by truck carriers were because of economic efficiency rather
than collusive activities as suggested by the structure performance hypothesis. Thus this
hypothesis is rejected based on the pooled data analysis and efficient structure hypothesis is
accepted.
The panel estimates for firms that stayed in the data set for the entire study are shown in
Table 3. Model 1 represents the estimated profit equation without categorizing the carriers by
commodity groups, regions, or years while Model 2 represents the estimated profit equation of
carriers by commodity groups, regions, and years. The results from Models 1 and 2 show the
market share and cash and equivalent variables had a significant impact on the profits of firms
that operated during the study. Model 2 results show the variable Sdum1, which represents the
1994-1996 pooled data period, also impacted profits made by the firms. This result implies the
time period in which the carriers operated played a major role in determining firm profits. These
results further indicate that profits made by firms in the data set were based on them being more
efficient than their competitors during the study. Thus, the results of this analysis still support the
efficient structure hypothesis rather than the structure performance hypothesis.