The stock market has climbed roughly 20 percent year-to-date, so who's driving the rally?
Not retail investors at Charles Schwab, according to CEO Walter Bettinger. In an interview with "Closing Bell" at the Schwab IMPACT 2013 investor conference, Bettinger said his clients are not pouring into the equity market.
(Read more: The one thing that worries Schwab investing pro)
"Our clients are engaged, but they're very cautious about the markets overall," Bettinger said, adding only about half of his clients think now is a good time to be make additional investments in equities.
"They are not trading, but they are planning. They are putting together strategies," he said. "They are executing in the long term as opposed to try and time markets and move in and out."
(Read more: Why technicians see red flags for stocks)
Institutional investors could be helping to send markets higher, but Bettinger thinks the Federal Reserve's $85 billion monthly bond-purchase program is the real catalyst. The Fed's bond-buying program has kept Treasury yields low, sending investors searching for yield, including droves of baby boomers whose retirement savings took a hit during the financial crisis.
"They built their retirement plans anticipating they'd make 3-, 4- or 5-percent interest on their money and that's not out there unless you go into dividends or equities or some other aggressive type of investment," Bettinger said. "So you've got a big influx of people who need income for retirement and where do they find it? They're not finding it in the traditional places."
In turn, Bettinger said investors are searching for yield in a market where the Fed controls rates—but they're worried about what will happen when the central bank decides to dial back its asset-purchase program. According to a recent survey of Schwab clients, two-thirds predicted a market correction within the next nine months, Bettinger said.
"People who have a long-term view know that we're in a bubble environment due to the Fed. They're not quite sure how it's going to end," he said. "We're in uncharted territory."
—By CNBC's Drew Sandholm. Follow him on Twitter @DrewSandholm.
