Why do people join trade unions? The impact of workplace union density on union recruitment

In this study the reasons for joining a trade union are analyzed statistically using high quality data from Statistics Denmark comprising the entire Danish workforce combined with European Social Survey data from rounds 1-3. These data enables measuring the effect of union density at the workplace level on union recruitment, which is not done before. Workplace union density is taken to measure the strength of the workplace’s custom of being union member creating an instrumental incentive to join the union. Self-placement on a political left-right scale measures political attitude taken to be a value rational motive. The statistical results indicate that the most important predictor of joining the union is workplace union density and only in a secondary manner does political attitude matter. It is concluded that the normative pressure of one’s colleagues is the dominating reason for joining a trade union.