NEW YORK » Slow down markets, you move too fast. The nation’s newest stock exchange has arrived, one that is looking to slow down high-frequency traders by putting speed bumps in their way.

The IEX Group won approval from the Securities and Exchange Commission on Friday to become a national stock exchange, following months of arguments with hedge funds and high-speed traders.

One of IEX’s hallmarks is imposing a delay of 350 millionths of a second on orders. That speed bump is meant to limit the influence of high-speed traders, which critics say reap unfair profits at the expense of longer-term investors, including pension funds and mutual funds held in 401(k) accounts.

“We are grateful and humbled by the support we’ve received from the investor community,” IEX Chief Executive Officer Brad Katsuyama said in a statement. “Without it, we may have faced a different result.”

IEX and Katsuyama were featured in “Flash Boys,” a best-selling book by Michael Lewis that heightened critical attention on traders that make transactions in billionths of a second. Critics say these high-speed traders can ultimately force mom-and-pop and other slower investors to pay a higher price for stocks they purchase.

Opponents of IEX, including hedge funds and others, argued to the SEC that the speed bump could make price quotes for stocks stale and unreliable and could have unintended consequences. They also argued the delay would run against regulations related to “immediately accessible orders.”

The SEC said Friday that “a small delay will not prevent investors from accessing stock prices in a fair and efficient manner.” It said an intentional delay of less than one millisecond, or one thousandth of a second, is a “de minimis” amount of time.

The SEC also said it will conduct a study within two years about whether the speed bump is hurting the market or investors.