These were the 5 biggest companies in 2019 and here are the 5 biggest companies now

There are many different ways to measure the size of a company. Next to market capitalization, revenue may be the simplest measure to understand the relative importance of a business.

Investors can track the Fortune 500 as an annual ranking of the largest corporations in the United States based on their sales of goods and services. The regularly changing list can provide insight into how industry leaders are growing and which high-level themes are shaping the economy.

Image source: Getty Images.

The list below shows the five largest US companies by revenue in 2019.

Data source: Fortune 500.

The latest ranking based on 2023 revenue features four of the same five names, but there have been some important changes.

Walmart is still on top as the largest company in the US, but Amazon is fast on its heels. The e-commerce leader doubled its top number from 2019 to climb to second place. Energy giant Exxon Mobil dropped from the list and was replaced by the healthcare leader UnitedHealth Group (UNH 1.23%).

Data source: Fortune 500.

A key takeaway is that technology is playing a bigger role in more sectors.

Walmart, for example, is investing heavily in its own e-commerce capabilities to better compete with Amazon. UnitedHealth incorporates technology through its mobile app and offers virtual care services to improve the patient experience. Even financial conglomerate Berkshire Hathaway is recognized as a leader in areas such as insurance and fintech that benefit from ongoing digital transformation.

Expect the list of largest companies to continue to evolve and further blur the lines between traditional sector classifications thanks to technology.