Social mobility is movement between social classes over time. It can be upward or downward, intragenerational (within one lifetime) or intergenerational (across generations). A factory worker's daughter who becomes a lawyer is upwardly mobile. A CEO's son who loses the family fortune is downwardly mobile.

Mobility rates vary by country. Nordic countries have high mobility. The United States has lower mobility than many Americans believe. Where you start often predicts where you end. Education, wealth, and social networks all shape mobility chances.

Types of mobility

• Vertical: moving up or down the class ladder
• Horizontal: moving between similar-status jobs
• Intergenerational: compared to parents' class
• Intragenerational: within one's own lifetime
• Structural: caused by changes in the economy, not individual effort

Structural mobility can lift whole groups. When factories opened in the 20th century, many working-class families moved into the middle class. When factories closed, mobility reversed. Individual effort matters, but so does the economy.