Opportunity Cost

TL;DR

Opportunity cost is the value of the next best alternative you give up when making a choice. Every decision involves a trade-off, and understanding this cost helps you make better choices. It's a fundamental concept in economics because resources are scarce.

1. The Mental Model

Imagine you have to pick just one thing from a list of good options. The opportunity cost is simply what you don't pick, specifically the best of what you didn't pick. It's about recognizing that making one choice means foregoing another.

2. The Core Material

In economics, we assume resources are scarce. This means there isn't enough of everything for everyone to have all they want, so choices must be made. When you choose to use a resource (like time, money, or land) for one purpose, you automatically give up the chance to use it for another.

The opportunity cost isn't just any alternative; it's the next best alternative that you sacrifice. For example, if you have three choices (A, B, and C) and you pick A, the opportunity cost isn't B and C, but rather whichever of B or C you valued more.

Understanding the Trade-off

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Every decision has a trade-off. When a government decides to fund healthcare, the trade-off might be less funding for education or infrastructure. When a business invests in a new machine, the trade-off might be that they can't also upgrade their delivery fleet.

Here’s a diagram showing how choices lead to opportunity costs:

graph LR
    A["Limited Resources (e.g., Money, Time)"] --> B{Make a Choice};
    B --> C["Chosen Option (e.g., Buy a new car)"];
    B --> D["Next Best Alternative (e.g., Save for a house)"];
    B --> E["Other Alternatives (e.g., Go on vacation)"];
    C -- "Value Gained" --> F["Benefit"];
    D -- "Value Foregone" --> G["Opportunity Cost"];

Implicit vs. Explicit Costs

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Opportunity cost often includes both explicit costs (actual money spent) and implicit costs (non-monetary costs like time or foregone earnings). For example, if you take a day off work to go to a concert, the explicit cost is the ticket price, but the implicit cost is the wages you didn't earn that day.

3. Worked Example

Let's say a student, Alex, has saved $1000. Alex has three options for how to use this money, ranked in order of personal preference:
1. Buy a new gaming console ($1000).
2. Invest the money in a savings account that yields $50 interest in a year.
3. Go on a weekend trip with friends ($1000).

If Alex chooses to buy the new gaming console, what's the opportunity cost?

The next best alternative for Alex was to invest the money in a savings account. So, the opportunity cost of buying the gaming console is the **