A correlation is a statistical measure which indicates the extent to which two variables fluctuate together. The two variables analysed here are the average labour market outcomes of native-born workers in a given year and education and experience group on the one hand, and the share of foreign-bom workers in that group on the other hand. It should be noted, however, that that a positive or negative correlation does not mean that a change in one of the two variables is the cause of the change in the other.