A recent article in MarketWatch ponders the question of why Warren Buffett has chosen to maintain and even add to his massive cash balances.

“One reason may lie in this chart,” the article argues, noting the trend in the ratio of market capitalization to GDP, a metric Buffett has described as “the best single measure of where valuations stand at any given moment:”

“As you can see,” the article explains, “the ratio suggests valuations are at a level not seen since the internet bubble two decades ago,” citing comments from Gary Evans of the Global Macro Monitor blog who warned that the current climate offers “very little to the upside,” and “very much to the downside.”

While Evans notes that the average person may not be a big holder of stocks, he argues that “the metric does give a heads up when the stock market becomes divorced from the underlying economic trend.”

As to whether the market can keep pushing ahead, Evans contends that “the jig is almost up and any further rise in inflation will put a stake through its heart.”