Non-cooperative Bargaining and Union Formation

We study a union formation decision problem when workers consist of two groups distinguished by different productivities. Workers may form either a joint union or two separate unions. The whole decision process is modelled as an extensive-form bargaining game. Workers form a joint union when the sizes or productivities of the groups are similar. In the first case, there is a wage differential which is more (less) than proportional to the productivity difference if the size of the more productive is smaller (larger) than that of the less productive. In the second case, there is no wage differential.