The article examines how immigrants affect the job market in California from 1960 to 2005. By analyzing the employment response to immigration based on skill levels, the study shows that immigrants and native workers are not always interchangeable. This means that immigrants do not always compete with natives for jobs. The findings suggest that immigrants can either boost or reduce the demand for native workers, depending on their skill levels. The study also supports the idea that immigrants and natives in the same education and experience groups do not always have the same impact on wages and employment.