Apple Inc. (NASDAQ:AAPL)’s market cap fell below the $400 billion mark today, according to CNET. Shares of Apple fell 2 percent today, pushing the company’s market cap to around $365.5 billion, which is the lowest valuation the company has had since late 2011. The stock has been declining in value ever since its record high of $705 per share in September. Within the past six months, shares of Apple Inc. (NASDAQ:AAPL) have fallen more than 37 percent.

Apple logo

The decline in valuation means Exxon Mobil Corporation (NYSE:XOM) has retaken its position as the most valuable company in the world. The oil giant’s market cap was at $399 billion, just a little higher than Apple’s valuation after its stock price fell.

Business Insider pointed out that as the economy starts to shift, Wall Street is beginning to look at Apple in a different way. Joe Weisenthal and Matthew Boesler contend that shares of Apple Inc. (NASDAQ:AAPL) were once seen as something of a commodity, much like gold. Then as the global economic crisis began to fade, the stock began to fall because it was less of a unique, valuable asset and more of just a regular, run-of-the-mill stock.

And Mark Dow also noted something interesting in relation to Apple Inc. (NASDAQ:AAPL)’s similarity to gold. He blogged about and tweeted a chart showing how Apple Inc. (NASDAQ:AAPL)’s stock compares to the price of gold over the past year. The two show a remarkably similar behavior pattern over the last 12 months.

Billionaire investor Warren Buffett also weighed in today about Apple Inc. (NASDAQ:AAPL)’s valuation. He said CEO Tim Cook should ignore David Einhorn’s push to issue perpetual preferred stock and buy the company’s stock back instead. According to Buffett, CEOs can’t worry about trying to push the company’s stock price back up every day. Instead, he advised that it makes more sense to buy back stock while it’s cheap. Buffett pointed out that his own Berkshire Hathaway Inc. (NYSE:BRK.A) (NYSE:BRK.B)’s stock dropped 50 percent in its history.

“When that happens, if you’ve got money, you buy it,” Buffett said.