Is Warren Buffett running out of acquisition ideas?

Buffett’s Berkshire Hathaway BRK.B, -0.89% closed the third quarter with $84.8 billion in cash, a gain of some $13 billion during the course of 2016.

Buffett over the years has not been shy about using the cash spit off from his vast array of holdings to buy companies, such as his most recent acquiree, Precision Castparts. Even excluding the $20 billion he has said he likes to keep as a cushion, Buffett has plenty of firepower to deploy.

In the quarterly report, Berkshire Hathaway says its “long-held acquisition strategy is to acquire businesses at sensible prices that have consistent earning power, good returns on equity and able and honest management.”

The question then is which of those metrics is proving most troublesome.

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Valuation certainly isn’t ideal. Though the S&P 500 SPX, -0.72% has closed lower for nine straight sessions, it’s only 5% below record highs. The current price-to-trailing earnings ratio of the S&P 500, around 24, is well above historic levels around 14.

Buffett’s hometown newspaper, the Omaha World-Herald, threw out a range of possible acquisition targets, ranging from Dr Pepper Snapple to Estee Lauder. But the paper conceded no one really has a good record of predicting acquisitions. And if anyone is playing the long game, Buffett and co-pilot Charlie Munger have to qualify.

In any case, Buffett’s own portfolio might give him cause to pause, even considering that the company’s operating profit grew during the quarter.

Take the industrial products unit that Precision Castparts is in. “Generally, these businesses were negatively affected by a combination of weaker customer demand and price and mix changes and increased restructuring costs, partly offset by the impacts of cost containment initiatives and lower average material prices,” Berkshire Hathaway reported. “We expect the prevailing market conditions to continue during the remainder of 2016 and we may take additional cost containment actions in response to further slowdowns in customer demand.”

The Burlington Northern Santa Fe railroad business is facing declining volumes, mostly from the troubles in the coal business, and it’s facing more difficulties ahead as the big soybean export boom — which boosted U.S. GDP in the third quarter — tails off.

The big boom in car and pickup trucks sales, which benefits both the Geico insurance as well as the railroad business, also might be nearing an end.