Castles and Kosack found that most immigrants in Britain were in low-paid, low-skilled jobs or unemployed. They argued that capitalism needs a "reserve army of labour" to keep wages low and weaken worker power. After WWII, European countries relied on immigrant labour, placing them at the bottom of the working class. This divide benefited the ruling class by suppressing wages, using "divide-and-rule" tactics, and scapegoating immigrants for unemployment, diverting attention from capitalism as the real cause of inequality and weakening worker unity.