The argument was over cash. Ever since the financial crisis, corporations have hoarded an increasing amount. The pile reached $2.2 trillion at the end of last year, up from $1.5 trillion at the end of 2007, according to data from the Federal Reserve. (First quarter data is due out later this week.) That may have made sense during the financial crisis and its immediate wake. But as corporate profits have rebounded the question was why weren’t companies using that money to make hires or open new plants or expand their business somehow.

That morphed into this Republican talking point: Companies weren’t spending money because of Obama. The President had pushed through banking reform, instituted the healthcare law and threatened to raise taxes on the wealthy. Conservatives argued that those moves and the threat of more were discouraging companies from investing in the U.S. economy, resulting in fewer hires and an anemic recovery.

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But a new study, Multinationals and the High Cash Hoarding Puzzle, released this week by the National Bureau of Economic Research refutes the idea that either taxes or regulation have played a part in the growing corporate cash hoards. The study, which is authored by two Georgetown economics professors, Lee Pinkowitz and Rohan Williamson, and Rene Stulz from Ohio State, looked at U.S. corporate cash holdings since the 1950s, in addition to the cash holding habits of companies in 45 other nations. And they didn’t just look at absolute cash, but cash as a percentage of assets to compensate for the fact that U.S. companies are larger than they used to be.

In general, what they found is that corporate cash has gone up, and is higher at U.S. companies than similar overseas firms. But the study also found that the biggest increase in corporate cash actually came in the early 2000s. It has grown much slower since the financial crisis.

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On regulation, the professors first looked at utilities, one of the most regulated industries. Yet, they said utilities generally had less cash than their model predicted they would if regulation was a big part of the cash equation. Next, the professors then divided the universe of U.S. companies they were looking at into those that were most and least affected by Sarbanes-Oxley, the accounting rules that came out of the early 2000s dot.com/Enron stock market bust. Here, again, they found no evidence that regulation matters when it comes to cash holdings. Companies that were most impacted by Sar-Box didn’t tend to hold more cash than those that were not.

On taxes, some have argued that the growing amount of cash on corporate balance sheets is a result of the fact that companies would have to pay taxes if they were to bring cash that they earned abroad back to the U.S. Since they don’t want to pay the higher taxes, companies leave the money overseas, even if they don’t have anywhere to invest it. But the professors looked at the two-year corporate tax holiday on foreign earnings of the early 2000s and found that it did little to bring down overall corporate cash holdings. What’s more, the professors found that while U.S. multinationals did hold more cash than companies that made most of their money domestically, the same was true in other countries, not all of which have different tax treatments for earnings made overseas.

So why do companies hold more cash than they used to? One of the most interesting things the professors found is a divergence between the cash held by public companies and the cash held by private companies. For decades, as a percentage of assets that figure used to be about the same. But in 1998 those lines diverged. Cash at public companies (the solid black line to the right) took off. Cash at private companies (the dotted line) actually dropped. Why would that be? Co-author Williamson thinks the fact that there are fewer corporate raiders than there used to be policing how much cash public companies hang on to. “In the 1980s we had Kirk Kerkorian and others trying to take over companies for their cash,” says Williamson. “Until recently, there’s been no real pressure on Apple or Google or other high-tech companies to pay out their cash.”

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But the bigger reason may be this: In the wake of dot.com bust and the financial crisis, investors have wanted more safety. In an earlier study, Williamson found that in the first half of the 2000s, investors tended to gravitate toward companies with bigger cash hoards. The rising stock values may have given corporate executives the incentive to hold onto larger and larger piles of cash. Private companies on the other hand wouldn’t have gotten the same benefit for holding cash, which may explain the divergence.

But the real bottom line appears to be that it is the market that is driving the rising cash hoards, not Obama or the government. Unfortunately, the invisible hand is harder to move.