Hillary Clinton is set to propose a tax hike on investors that her campaign camp says will encourage companies and investors to think more long-term about opportunities for economic growth. In a speech Friday afternoon at the New York University Stern School of Business, the presidential candidate is expected to lay out a proposal for taxing short-term investments more heavily, and, in turn, create incentive for longer term investments that might benefit worker productivity, job prospects, and wages.

Economists have begun to highlight the role that corporate buybacks of large chunks of a company's own stock play in fueling "short-termism" of hedge funds and activist investors. Sen. Bernie Sanders of Vermont -- who is challenging Clinton for the 2016 Democratic presidential nomination -- addressed stock repurchasing programs in an editorial last month in the Boston Globe, and Clinton brought up the subject in a speech last week.

Earlier this week, Deutsche Bank global equity strategist Binky Chadha issued a research note to investors in which he concluded that the steady rise of U.S. stocks in the last six years is largely due to corporations repurchasing their own stock.

Stock buybacks are a way for corporations to reward investors because they provide an immediate boost to share values. But detractors point out that the repurchases often come at the expense of corporate investments that benefit the broader economy, such as in new hires and business expansion.

Although companies have engaged in stock buybacks since the 1980s, this is the first presidential campaign in which the topic has come to the fore, said William Lazonick, an economics professor at the University of Massachusetts, Lowell.

Lazonick would know. He's a leading expert on the relationship between buybacks, worker productivity, and the development of a thriving middle class. Last year, he wrote a seminal, prize-winning paper in Harvard Business Review, "Profits Without Prosperity," that sparked a lot of buzz around a topic that's largely remained under the radar for decades.

A major critic of buybacks, Lazonick would welcome reforms to a practice that he says manipulates the stock market, and starves companies and employees of important investments in training and education. But he just doesn't think that changing the tax code to encourage longer-term holdings is the way to do it.

"It's making a pretense of addressing the problem. The accountants, and everyone else will still find ways around it," he said. "It's not going to solve the problem of keeping money in companies."

Lazonick would rather see policymakers aim squarely at Securities and Exchange Commission regulations that allow corporations to buy large quantities of their own stock in the first place. In that sense, he said, the solution is easy: "Call it manipulation, and tell companies they can't do it."

Some finance experts question whether a higher tax on short-term investments would help sharpen corporate America’s focus on the long term. Anant Sundaram, a finance professor at Dartmouth College’s Tuck School of Business, says the policy could have unintended consequences for investors large and small. “The one downside of lengthening the holding period could be to significantly disadvantage capital-raising in the high-growth, venture capital type areas of the economy,” Sundaram notes. More than a few years would be "a long time to expect someone to hold on to even an Uber or an Airbnb, let alone smaller startups," he says.

Mom and pop investors could suffer too. Especially “for those who are trying to achieve appropriate asset allocation in their personal portfolios as they get older, and their holding period start to shrink. They could face much higher tax bills,” he says.