Contribution of independent variables to pre-WWII growth

Contribution of independent variables to membership growth of Dutch trade unions before WWII as predicted by Van den Berg’s model 4 (Van den Berg 1995: 102). ΔPt = change in consumer prices (positive effect on predicted membership growth); ΔWt = change in gross nominal wages (positive effect); Ut = unemployment (positive effect); Ut-1 = unemployment, previous year (negative effect); St-1 = number of strikes, previous year (negative effect). Calculated using data from Van den Berg (1995: 112-3). Note that the model includes a constant value of 26.8. This implies that the total contribution of independent variables in a given year can be negative and still result in a positive value for predicted growth. Dashed lines represent years with strong membership growth. Chart dirkmjk.