Measuring and decomposing productivity change in the presence of mergers

Managers and policymakers often encourage mergers and acquisitions of companies with the aim of increasing the productivity of the involved firms. However, problems with the measurement of productivity change usually occur when analyzing companies that merged during the period under consideration: while only individual predecessor firms exist in the base period, in the following period only the integrated company is observable. We therefore propose a new adaptation of the Malmquist index that is appropriate in the presence of mergers, which also allows for a detailed analysis of their effects on productivity change. Moreover, we believe that our methodological approach provides a useful widely applicable tool to identify the contribution of past mergers to productivity growth. We illustrate our merger consistent productivity decomposition, by using a sample of Japanese water supply systems observed in 2003, and the resulting consolidated and non-consolidated systems observed in 2009. On average, we find that mergers contributed positively to productivity change and that our merger consistent decomposition contributes to a better understanding of the determinants of productivity performance in the Japanese water sector.