Productivity development of Norwegian electricity distribution utilities

When regulating electricity distribution utilities, estimates of the past productivity improvement performance are very important for future requirements. A piecewise linear frontier technology, reflecting observed best practice, accommodating the multi-output nature of distribution utilities is specified. A Malmquist index and its components, shift in frontier technology and change in efficiency, have been calculated for the period 1983 to 1989. The main results are a positive productivity growth averaging nearly 2% per year, and that this is mainly due to frontier technology shift. Outliers are scrutinised, but do not influence results for non-outliers.