## How Individuals Make Choices Based on Their Budget Constraints

Read this section to understand the concept of a budget constraint and how people make decisions when faced with this type of constraint. In economics, a budget constraint is a model that represents two possible things to choose from when spending some income. For example, suppose that you are a store manager and you have $100 to spend on two things for decorations for the store: flower arrangements at$10 each and posters at $5 each. A budget constraint for$100 will then be the different combinations with different number of flower arrangements and posters.

### The Concept of Opportunity Cost

Economists use the term opportunity cost to indicate what must be given up to obtain something that is desired. The idea behind opportunity cost is that the cost of one item is the lost opportunity to do or consume something else; in short, opportunity cost is the value of the next best alternative. For Alphonso, the opportunity cost of a burger is the four bus tickets he would have to give up. He would decide whether or not to choose the burger depending on whether the value of the burger exceeds the value of the forgone alternative – in this case, bus tickets. Since people must choose, they inevitably face tradeoffs in which they have to give up things they desire to get other things they desire more.

A fundamental principle of economics is that every choice has an opportunity cost. If you sleep through your economics class (not recommended, by the way), the opportunity cost is the learning you miss from not attending class. If you spend your income on video games, you cannot spend it on movies. If you choose to marry one person, you give up the opportunity to marry anyone else. In short, opportunity cost is all around us and part of human existence.

The following Work It Out feature shows a step-by-step analysis of a budget constraint calculation. Read through it to understand another important concept – slope – that is further explained in the appendix The Use of Mathematics in Principles of Economics.