Cesarini's Law is a principle in economics that suggests individuals tend to spend a portion of unexpected income, such as lottery winnings or tax refunds, rather than saving it all. This behavior highlights how people often prioritize immediate gratification over long-term financial planning. The law is named after Francesco Cesarini, an economist who studied consumer behavior. His research indicated that about 20-30% of unexpected income is typically spent on consumption, while the remainder may be saved or invested. This insight helps economists understand spending patterns and the impact of sudden financial changes on the economy.