When regional growth studies are conducted, a common measure of economic growth is the wage sum. One reason for this may be the limited access to GDP (Gross Domestic Product) data on regional level. However, in Sweden there exists GDP data on municipal level, which enables studies where the effects of using GDP data or wage data can be compared. The aim of the present study is to investigate the difference the use of the measures GMP (Gross Municipal Product) and the sum of wages has on growth models. Since the two measures are similar but not identical the choice of measure of growth can influence the conclusions of an investigation. This might lead to contradictory results on for instance how knowledge activities influence economic growth. Therefore an empirical investigation on Swedish data is conducted in order test whether or not the use of GMP and wage sum respectively in a regional economic growth model give rise to different results. GMP and wage sum data on municipality level are used to calculate two output measures; percentage change and percentage change per employee in two different time periods. Local, intra-regional and inter-regional accessibility to R&D are the main explanatory variables used in the model. The results indicate that the models using any version of change in wage sum as dependent variable has more statistically significant parameters than the corresponding model using change in GMP.