These were the 5 biggest companies in 2004 and here are the 5 biggest companies now

The world has changed a lot in the last 20 years, and that certainly applies to the business world as well.

Once upon a time, the American economy was dominated by banks, oil companies, and manufacturers. These days, the tech sector reigns supreme, as “Magnificent Seven” makes clear.

However, it can be informative to take a drive back and see what has changed. This reminds you that nothing lasts forever in business and is a useful way to study what worked and what didn’t.

Image source: Getty Images.

With that in mind, the list below shows the five largest US companies by revenue in 2004.

Source: Fortune 500

If you’re familiar with the stock market and economics of 20 years ago, that list might not come as much of a surprise. Walmart dominated the retail sector and Exxon was the main oil major.

What’s notable about that list, however, is how all of these companies, except Walmart, have weakened since then. In fact, all five of these stocks underperformed S&P 500 in the last 20 years. General Motors filed for bankruptcy protection in 2009, and Ford almost followed suit. General Electric was dismantled after years of mismanagement. Exxon didn’t suffer a major meltdown, but the oil sector fell out of favor with growing electric vehicles (EVs).

Now let’s look at the five largest companies by revenue today.

Source: Fortune 500

Impressively, Walmart has retained its top spot, although Amazon is likely to overtake it in the next few years.

The other companies tell a story about how the economy has changed. Amazon and Apple, at No. 2 and No. 3, are consumer-driven technology companies, while healthcare makes an appearance at No. 4 in the form of insurance. Warren Buffett’s Berkshire Hathaway rounds out the list, and Berkshire’s main business is insurance. He also owns a large stake in Apple, although that doesn’t count in his income.

On the other hand, oil and gas and manufacturing have declined, as evidenced by the absence of companies such as ExxonMobil, GM, Ford and GE.

Will technology, healthcare and insurance remain ascendant or will other industries replace them? Companies at the top of the Fortune 500 are worth keeping an eye on as the list continues to evolve.