“Critics of the leveraged and inverse products state these ETFs can both exacerbate intraday moves to the downside as well as artificially lift stocks into an already-strong close. There is no publicly available data to support that assumption, at least as far as I have seen,” Colas said.

“Anecdotes abound; proof seems in short supply. What is provable, as the numbers shown above indicate, is that this segment of the ETF marketplace is very small relative to almost any other category,” the strategist wrote. “Anything is possible, of course, but the assertion that $36 billion of ETF products can consistently determine the intraday course of U.S. stock markets needs more substantiation than is currently on offer.”

Scott Burns, head of ETF research at Morningstar, in telephone interview Tuesday said he hopes the Senate subcommittee hearing can clear up some of the “boogieman” accusations leveled at ETFs that they increase market volatility and correlations. [Leveraged ETFs: Tail Not Wagging the Dog]

ETFs are the “lowest-cost, most liquid, transparent and tax-efficient vehicles available for investors,” Burns said.

ETFs have grown amid volatile markets, but that doesn’t mean they’re they culprit, he added. Some of the negative media stories on ETFs are “half-substantiated” and fail to link correlation and causation, the analyst said.

Individuals scheduled to testify at the hearing Wednesday include Noel Archard, a managing director at BlackRock ETF manager iShares, and Harold Bradley, the chief investment officer at the Kauffman Foundation, according to the report.

Bradley is the co-author of a 2010 report alleging ETFs the financial products are distorting markets and curtailing new companies’ access to capital.

Nasdaq executive Eric Noll and Eileen Rominger, the director of the Securities and Exchange Commission’s Investment Management division, will also testify, according to the Senate’s website.

The hearing is entitled “Market Microstructure: Examination of Exchange-Traded Funds (ETFs).”