For decades, Polish Americans have been the subject of derogatory jokes originating in anti-immigrant stereotypes that had developed in the U.S. before the 1920s. During the Partitions of Poland, Polish immigrants came to the United States in considerable numbers, fleeing mass persecution at home. They were taking the only jobs available to them, usually requiring physical labor. The same ethnic and job-related stereotypes persisted even as Polish Americans joined the middle class in the mid-20th century. "The constant derision, often publicly disseminated through the mass media, caused serious identity crises, feeling of inadequacy, and low self-esteem for many Polish Americans." In spite of the plight of Polish people under Cold War communism, negative stereotypes about Polish Americans endured.