Components of GDP

GDP is important as a headline number, a big picture view of a country’s economic performance. However, we can break it down into smaller pieces, each clearly connected to a different activity. Common transactions with categorizations that are tricky or counterintuitive will be clearly outlined by the end of this subchapter.

Calculating GDP

In the United States data for this GDP is collected by the Bureau of Economic Analysis, a part of the Department of Commerce. The relevant tables are referred to as the National Income and Product Accounts (NIPAs).

There are three methods used to calculate GDP.

1. Income approach : Adding up all income earned regardless of source, with adjustments for activities performed in other countries. Remember location of the economic activity is what matters, not the citizenship or home country of the company.

2. Production approach (also called the valued added method) : Adding up the value added for each company. The value added is equal to the value of goods and services sold minus the costs of any direct inputs. Direct inputs are parts and resources used in production and not things like labor.

3. Expenditure method : Adding up all of the spending in the economy, using categories from the expenditure formula.

Regardless of the method, the value should be the same. If there are differences in calculations, there is usually a row in government data tables called the “statistical discrepancy.” This is true of a few other economic identities that we have, items that are not just theories but must be exactly equal to each other if everything is measured correctly.

When it comes to actual measurement, the value added approach is the primary method and the one that we need to know more about. For each firm, we need the revenue from sales and the cost of any inputs outside of labor, no matter if they are intermediate goods or resources. The value added for each firm is revenue minus the cost of inputs.

The value added gives the total amount firm contributed to GDP through their production process plus the value of labor used. It must be strongly emphasized that labor costs are not taken out, they are meant to be part of value added for a firm.

Adding together value added for all firms located in the United States gives a production-side measure of GDP. This approach does make it easier to deal with some of the peculiarities and details that can be troublesome, international trade in intermediate goods and inventories in particular. If we only measure final goods, intermediate and used goods need to be included in exports and imports so that they are correctly “taken out” from the final value of GDP.

All that being said, conceptually the expenditure formula is what helps us to understand and model GDP.

Expenditure formula for GDP

The expenditure method uses the following formula

$$\begin{array}{rl}Y& =C+I+G+X-M\\ & \text{or}\\ Y& =C+I+G+NX\end{array}$$

These are the most important equations in the entire course. Some piece of this is connected to basically all other important markets, models and discussions.

Here are the parts of the GDP equation

• C : consumption
• I : investment
• G : government spending
• X : exports
• M : imports
• NX = X-M : net exports

In some ways GDP discussions are more about accounting than economics. While the general rules are mostly straightforward, there are some little details that need to be covered. With that in mind, we can discuss what is included in each piece of that equation.

Consumption

Consumption covers all spending on final goods and services by households, with the sole exception of housing. Services are their own category treated separately from all goods. Goods are split based on how long they are expected to last.

Definitions

Durable good

A good with an average life of at least three years

Non-durable goods

A good with an average life of under three years

Durable goods will include items such as furniture, appliances and cars. These are usually larger purchases that are made less frequently.

Non-durable goods include things that are often purchased on a weekly or monthly basis. Gasoline, food, cleaning products, pharmaceuticals, and disposable paper products are all examples of non-durable goods.

The major counterintuitive classification is clothing and footwear, which is a more frequent purchase that we may expect to last longer than three years. It is classified as a non-durable good.

The table below shows recent real values for the pieces of consumption, from the Bureau of Economic Analysis. They are measured in billions of 2017 dollars.

	2023	2024	2025
Personal consumption expenditures	15627.8	16088.5	16515
Goods	5316.3	5466.8	5641.6
Durable goods	1982.8	2059.6	2132.1
Nondurable goods	3341.3	3417.3	3520.6
Services	10331.8	10642.1	10897.1

Investment

Investment is spending by private businesses on capital and inventories, as well as household spending on housing. Remember that only newly produced goods count and not used goods, so housing only counts at all if you buy a new house or make improvements to an existing house.

The trickiest part of investment is inventories, goods made but not sold in the same year. Imagine items still in a warehouse or the backroom of a store on January 1 in any year. They were made the year before but the business can still sell them.

In whatever year they are purchased, consumption goes up and inventories go down by the same amount. Thus the transaction has no impact on GDP for that year.

Inventories also will include intermediate goods that are made but not sold. In whatever year they are sold we have a negative entry for investment. That removes the part of the final sale that was not produced in that year.

Inventories may sound complicated, but their actual measurement is simplified considerably by just tracking the total value of inventories. Once something ends up in inventories, and it is a new year, it no longer matters what location and what year it was actually made. Using the inventory, whether it is part of a production process, sold directly to consumers or becomes investment as a capital purchase, always leads to a negative entry for $I$ in our GDP accounting.

Here is a table providing recent real values for the categories of investment, measured in billions of 2017 dollars.

	2023	2024	2025
Gross private domestic investment	4219.5	4346.5	4434.6
Fixed investment	4140.4	4264	4380.1
Nonresidential	3418.6	3518.9	3666
Structures	686.4	694	659.2
Equipment	1267	1311.5	1419.5
Intellectual property products	1460	1511	1598.3
Residential	766.1	790.4	773.2
Change in private inventories	47.4	43.5	29

Government spending

Government spending covers all final goods and services as well as any investment by the government. Everything that would count as consumption for households or as investment for businesses counts as government spending when done by the government. Even though we will mostly focus discussion on the federal government, this category includes all levels, state and local as well.

This includes spending on the military, wages for all government employees, construction of buildings, purchases of vehicles. Every direct purchase counts, regardless of if it is used by the government or given to a business, other level of government or household.

The main adjustment for government spending concerns transfer payments (TR). If the government gives money to another party instead of spending it directly, that does not count. Transfer payments include a lot of sizable programs, such as Social Security, unemployment benefits, and food stamps.

Regardless of how funds are moved around, what category a transaction fits into is primarily determined by who makes the actual purchase.

Decisions about government spending and taxation are categorized as fiscal policy, which will be discussed at length in future subchapters.

Here is a table providing recent real values for the categories of government spending, measured in billions of 2017 dollars.

Government current expenditures	3800.7	3945.3	3991.1
Federal	1471.4	1527.4	1509.8
National defense	830.5	863.5	873.6
Nondefense	640.9	663.9	635.9
State and local	2329.2	2417.8	2480.2

Exports and imports

If we have no trade, that is a closed economy. If we include these items and allow for trade, we call it an open economy.

Exports are goods produced in our country but sold in another. For example a Hershey’s chocolate bar made in the United States and sold in the UK. It is domestic production, so it should count, thus these transactions need to be added back in. This is why exports are added to GDP.

Imports are goods produced in another country but purchased in ours. For example a Cadbury’s chocolate bar made in the UK and sold in the US. Nothing was made domestically, so it should not appear in GDP. The purchase would show up as consumption ($C$), so counting it in imports ($M$) cancels that out. That is why imports are subtracted from GDP.

Goods crossing borders do introduce some complicated details. In particular intermediate goods do count for $X$ and $M$. The logic is very similar to our discussion of inventories. Instead of being due to differences in years, this adjustment is about differences in location. Including intermediates is equivalent to removing the foreign produced piece of any sale of a final good, thus avoiding double counting.

Similarly, if we send an intermediate good abroad, it was still made in the United States and should count. Here the worry is not double counting, but rather not counting the good at all.

Sometimes we simplify separating exports and imports and just worry about the balance of trade, exports minus imports ($NX=X-M$). If net exports are positive, exports are greater than imports and we sell more abroad than we buy from other countries. If net exports are negative, imports are greater than exports and we buy more from other countries than we sell abroad.

We will set aside open economy considerations until Chapter 6. This will allow us to focus on fundamentals first, before introducing the complications of international trade and financial flows.

Here is a table providing recent real values for the net export (trade) balance and categories of exports and imports, measured in billions of 2017 dollars.

	2023	2024	2025
Net exports of goods and services	-925.2	-1032.6	-1086
Exports	2541	2633.6	2679.5
Goods	1696	1730.6	1762.4
Services	848.6	905.3	919.6
Imports	3466.2	3666.2	3765.5
Goods	2825.4	2971	3044.4
Services	641.1	693.9	718.2

Note on recent data

Subcategories may not add up exactly to higher level definitions, because the conversion from nominal to real is done on each row separately using an averaging method called chain-weighting. You are not responsible for understanding how this occurs, but if you look at official tables you may see the term.