In Greece, the participation rate (as percentage of working-age population) in 1998 for men aged 15-24 was 44.3%; aged 24-54, 94.2%; and aged 55-64, 57%. For the United States, these numbers were 68.4%, 91.8%, and 68.1%. In Greece, the corresponding ?gures for women were 37.3%, 59.4%, 24.4%, and for women in the United States, 63.3%, 76.5%, and 51.2%. What do you think explains these cross-country differences?