So just like we can talk about nominal interest and real interest, we can discuss nominal income and real income. Just like with interest, the difference between the nominal and the real is going to have to do with inflation. When we're discussing nominal income, nominal income is the actual number of dollars you receive. So when you go to work and they pay you your salary of $10 an hour, that $10 an hour is your nominal income, right? The number of dollars received as wages or salary; rent could be profit. Whatever type of income you have, right? So if you just have a job, we're talking about wages or salary, but if you're a landlord, it's rent; any of this is nominal income.
So when we talk about real income, we're adjusting that nominal income for inflation. It's adjusted for inflation. Remember how inflation affects our income is the same way it affects interest; it's going to make our purchasing power less. Real income measures the amount of goods you can buy. So if you're thinking about what you could buy in one year and what you could buy in another year, that would have to deal with your real income, your purchasing power of that money.
Let's go ahead and use a calculation for real income. We're going to take our nominal income, what we're earning, and we're going to divide it by the price index. This is the CPI. When we're talking about the price index, we're talking about the CPI here, and notice that it's normalized to 100. So if they give you the CPI as, say, 110, we would have to adjust it to be treated as 1.10, more of a decimal rather than a percentage here. A CPI of 110 means that prices are 1.1 times the level of what they were in the base year. So the base year would have had a CPI of 100, and now it's 110. That means we've increased by essentially 10% since the base year.
If nominal income increases at the same rate as the price index, then what happens to the real income? Think about it. If your nominal income is increasing, and the price level is increasing at the same rate, then your real income is going to stay constant because what's happening is if you're earning more money—say, you're getting a raise from $10 to $12 which is a 20% raise—but at the same time, the price of everything goes up by 20%, which is what it's saying here. If nominal income, your $10 wage going to $12 increases at the same rate as the price index, the prices of everything also went up by 20%, you can purchase just the same as before. Your real income is going to stay the same there.
In essence, the main formulas you're going to want to know here are how to calculate real income, which is just taking the nominal income divided by the price index, and you're also going to be able to calculate the change in your real income by noting the change in the nominal income and the change in the price level. We've got an example that we're going to practice using these formulas. Let's do that in the next video.