Utility reflects the satisfaction individuals gain from consuming goods and services. As income rises, people can afford more goods and services, increasing overall satisfaction. So, utility and income are related.  Economists often assume utility can be measured numerically to analyze the relationship between utility and income. They often assume most people experience diminishing marginal utility of income.

Diminishing marginal utility suggests that each additional dollar of income provides less satisfaction than before. The effect is not necessarily linear—the degree of diminishing marginal utility varies by income level and individual preferences. In other words, an initial increase in income significantly enhances well-being. However, subsequent increases lead to smaller gains in satisfaction. 

Also, an income loss is perceived to have a stronger impact on well-being than an equivalent income gain. This means a reduction in income leads to a larger drop in utility than the increase in utility generated by the same amount of additional income.

Understanding the diminishing marginal utility of income is essential for analyzing consumer behavior.