Why do Trade union members have different Atittudes towards immigration?

In Europe, union members' attitudes towards immigration are moderately tolerant when they are ideologically located on the political left. This behavior is different from that of non union members', whose attitude is restrictive. Ideological positions and attitudes draw a U-shaped pattern. At one extreme are the positions of the left-wing, associated with high union membership and moderately tolerant attitudes. At the other extreme are right-wing positions, with low union membership and restrictive attitudes. Factors that influence negative attitudes include unemployment, low wages, temporary job contracts and other forms of precarious employment. Competition for scarce jobs and welfare resources explains these attitudes. Nowadays, the economic crisis and unemployment contribute to restrictive attitudes towards immigration.