People who live or work in several European countries are building up pension rights in different systems, but often cannot see their total future pension income in one place. Lisa Brüggen, a professor at Maastricht University, said that pension amounts shown in Dutch and German systems are calculated differently. The issue particularly affects workers in construction, catering and transport, as well as people who move to the Netherlands from countries including Poland, Romania and Spain and later return home. The APB pension fund has about 18,000 retired members who have not claimed their money, including foreign nationals and Dutch people living abroad. The fund said privacy rules prevent it from independently tracing them.