5.12 : 预算约束 I

A budget constraint represents the various product combinations a consumer may purchase with their current income and prevailing prices.

For example, Nancy has a weekly budget of twenty dollars for snacks and skincare products. Snacks cost five dollars each, and skincare products are ten dollars each.

The budget constraint, as shown in the Table, is what Nancy can buy with her twenty dollars.

Graphically, the budget constraint is depicted and referred to as a budget line.

In Nancy's case, the x-axis represents the quantity of snacks, and the y-axis represents the quantity of skincare products.

If Nancy spends all twenty dollars on snacks, the x-intercept shows she can buy four units.

If she spends everything on skincare products, the y-intercept shows she can buy two units.

The two points are joined to get the budget line.

The tradeoff in her ability to afford these two products is the ratio of the two prices. Buying one less skin care product allows her to afford two additional snacks. If prices do not change, this tradeoff ratio remains constant across all affordable combinations of products purchased. This creates a straight-line budget curve.