Jack Bogle should be proud.

The founder of Vanguard, who has long advocated that investors take a simple approach to their portfolios by buying low-fee index funds and holding them for the very long term, seems to have taught his lesson well.

According to the asset-managing giant, which has taken in massive inflows in recent years as investors flock to passive investment strategies, its clients kept their wits about them in the recent turmoil on Wall Street, which saw the Dow Jones Industrial Average DJIA, -0.87% and the S&P 500 SPX, -1.11% last week enter correction territory for the first time in about two years.

“Vanguard investors are sticking to their long-term investment plans and tuning out the noise of the stock market volatility of the past few weeks,” the firm wrote in a news release. Citing data from its own Center for Investor Research, Vanguard added that “over the six-day period from Feb. 2 through Feb. 9, Vanguard found that 97% of households did not trade. Vanguard also found that trading on volatile days rarely exceeds 1% of households.”

The study looked at the activity of some 8 million U.S. investor households, including both individual investors and 401(k) investors. In comparison, while Vanguard investors stood pat, equity funds saw their largest weekly outflows on record amid the market turmoil.

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Over the past month, about $32.8 billion has flowed into all Vanguard funds, according to Morningstar Direct data, the most of any fund family.

One of Vanguard’s guiding principles is that investors should favor passive vehicles, which mimic the performance of underlying indexes like the S&P by holding the same securities as the index, and in the same proportion. This is in contrast to actively managed portfolios, where the components are selected at the discretion of a manager. Data have repeated showed that over the long term, basically no active managers are able to beat the overall market, particularly when fees are taken into account.

The firm also advocates extremely long-term investing, which lets investors ride out market cycles and get the benefit of compound interest. Vanguard managers have even turned down multimillion-dollar investments in its mutual funds if the potential client admits the position will be a short-term one, as the firm would rather discourage speculators than get the inflows (and resultant fees), according to spokesman Freddy Martino.

This ethos does seem ingrained in individual Vanguard investors, who sometimes dub themselves “Bogleheads” in acknowledgment of the founder’s investing principles.

According to data provided by Ben Johnson, director of global ETF research at Morningstar, investors in Vanguard exchange-traded funds hold them for significantly longer than funds sponsored by iShares or State Street Global Advisors, the other two ETF providers that make up the “big three” sponsors.

According to the data, which looks at the 20 largest ETFs by assets, the average holding period for a Vanguard fund is 462.5 days. For iShares, the average is significantly lower, at 262.4 days.

The shorter holding period doesn’t mean that the fund is operating incorrectly, or that the securities it offers exposure to are worse investments. All the above funds can be used as long-term holdings, but as Johnson notes, while some funds are favored for this purpose, others are more heavily used by traders as short-term positions.

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The SPDR S&P 500 ETF Trust SPY, -1.15% is the most prominent example. It is the oldest and largest ETF on the market, and it is viewed as one of the most liquidity securities of any type traded on Wall Street, meaning investors can easily open and close positions—including very large trades—without a major impact on the security’s price. For this reason, the SPY, as it is known for its ticker symbol, is a favorite tool for shorting the market, or hedging one’s portfolio.

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Another SSGA product, the SPDR Gold Shares GLD, +0.13% , serves a similar use in the commodity market; because of its higher liquidity, it is far more popular than other funds offering exposure to gold, even ones that charge lower expense ratios.

Similarly, two iShares products are trading favorites for both small-capitalization stocks and overseas equities: the iShares Russell 2000 ETF IWM, -0.26% and the iShares MSCI Emerging Markets ETF EEM, -0.78% both have average holding periods below 35 days, dragging down the overall average of iShares, the other major leader in passive products.

ETFs are widely used as a way to make quick adjustments to one’s portfolio because they can be traded intraday like a stock. That’s in contrast to mutual funds, which only trade and price at the end of a trading session. In fact, Vanguard’s Bogle turned down the opportunity to create the first ETF, saying he was concerned that their greater flexibility could lead to their overuse by traders, and that excessive trading can lead to lower returns.