When this bull market was born 10 years ago, just one of the most valuable companies in the market was a technology stock. Now, it's four out of five.
Back in March 2009, the biggest companies were familiar names with long histories in traditional industries like oil (Exxon Mobil) and makers of detergent and other household products (Procter & Gamble).
There is, however, one company that's among the most valuable today that was also among the Big Five back then: Microsoft.
These days, technology companies dominate the top five, as they do the market overall. After Microsoft, there's Apple, Amazon, and Google's parent company Alphabet. At the beginning of the bull market, Apple's iPhone was just two years old and Google had just released its Android operating system for smartphones.
Today, the iPhone accounts for most of Apple's revenue, helping Apple to become the first publicly traded company worth more than $1 trillion last year. Amazon quickly followed suit. Both now trade well below that level, and jockey with Microsoft for the most-valuable U.S. company title with valuations of around $800 million or higher.
The explosion of value in those four stocks reflects the great amount of cultural influence, wealth and power that has been accumulated by big technology companies over the past 10 years.
And Facebook, which didn't even become a publicly traded company until 2012, today is the No. 6 most valuable company in the U.S. with a valuation of nearly $500 billion.
The roster of the most valuable companies at the bull market's birth is a window into what the economy looked like a decade ago: Exxon Mobil, Walmart, Microsoft, Procter & Gamble and AT&T.
Those companies are hardly out of the picture today. They're all among 25 most valuable U.S. companies, and all but AT&T are in the prestigious 30-member club of the Dow Jones Industrial Average. And they've all had their share of change. For instance, Walmart has gotten heavily into online sales, and AT&T bought the media giant Time Warner.
Berkshire Hathaway rounds out the top five most valuable companies today. Edging out Facebook in the valuation contest, Warren Buffett's sprawling company continues to defy categorization.
While it still owns sizable stakes in other companies such as American Express, Coca-Cola and Wells Fargo, it also owns outright a number of big operating businesses including the insurer Geico and the Burlington Northern Santa Fe railroad.
Even for the folksy Oracle of Omaha, change has come over the years. Despite being a buddy of Microsoft co-founder Bill Gates, Buffett, who is widely considered one of the most prescient and successful investing gurus of all time, said for years he didn't understand the technology business well enough to invest in it.
According to his latest letter to shareholders last month, Berkshire currently owns 5.4 percent of Apple.