Final answer:
The shape of the total utility curve is determined by the principle of diminishing marginal utility. As more units of a good are consumed, the additional satisfaction decreases, causing the curve to level off after initially rising.
Step-by-step explanation:
The total utility curve is shaped by the economic principle of diminishing marginal utility. This principle posits that as a consumer consumes more units of a good or service, the additional satisfaction (marginal utility) gained from consuming each additional unit decreases.
In the context of a budget constraint, consumers make choices that maximize their total utility within their income limits, selecting combinations of goods that offer the highest satisfaction. Assuming a consumer like José who enjoys collecting T-shirts and watching movies, he will allocate his budget in a way that the last dollar spent on each good provides the same amount of marginal utility, which is known as equalizing the marginal utility per dollar spent. Therefore, as more of a good is consumed, the total utility increases at a decreasing rate, creating a curve that initially rises steeply and then levels off, reflecting the diminishing additional satisfaction of consuming more of the same item.