Rarely has it cost so much to purchase low-priced stocks.

With oil’s rebound helping U.S. energy producers recover from a 27 percent plunge, the least-expensive industry in the Standard & Poor’s 500 Index just became banks, where the median company trades at 17.6 times earnings from the past 12 months. That’s no bargain: only once has the cheapest sector commanded a higher valuation, a quarter century of data compiled by Bloomberg and Leuthold Group show.

The lack of bargains is another challenge facing investors after a six-year rally added $17 trillion to equity prices. Alternatives to stocks are already scarce with bond yields hovering near record lows. Now, pickings are getting slimmer in equities just as profit growth has ground to a halt and the Federal Reserve is preparing to raise interest rates.

“Investors are being dragged kicking and screaming into the stock market because, while valuations are not cheap, there really aren’t any better options,” Tom Mangan, who helps oversee about $6.4 billion as a money manager at James Investment Research in Xenia, Ohio, said by phone. “Investors will have to identify undervalued stocks individually, not by sector.”

While elevated, the U.S. stock market’s overall valuation isn’t far from its historical average. The S&P 500’s price-earnings ratio is 18.8, about 2.4 points above the 10-year mean and 38 percent below its 1999 record.

Futures on the S&P 500 expiring next month slipped 0.3 percent at 10:10 a.m. in London.

Stock Prices

Below the surface is a valuation pattern traceable to the bull market’s breadth. Since so few companies have been left behind since 2009, almost nothing is cheap.

“You’re seeing commonality in stocks right now, particularly those in the lowest-valuation sectors,” said David Kahn, managing director at Convergent Wealth Advisors in Los Angeles. The firm oversees about $8.4 billion. “They, in particular, tend to benefit less from a low interest rate.”

While banks became cheapest in March, they’ve recently come back into favor with investors anticipating an interest rate increase by the Federal Reserve. Financial firms have risen in four of the last five weeks.