Most investors are ignorant about the management style of the funds they are buying, according to Andy Surrey, senior national development manager at Vanguard.
Mr Surrey, who is responsible for promoting the active range of funds offered by Vanguard in the UK, said most fund managers have a particular style that they use, value or growth or quality or momentum.
He said most investors decide they want, for example, a global equity fund, but don't know about the style.
Mr Surrey said: "They decide they want a fund, and look at the recent performance, but don't look at whether recent good performance is the result of that style being in favour, and the style used by the fund manager then falls from favour, the fund underperforms."
He said the funds run at Vanguard aim to balance the various styles.
The three Vanguard funds approaching their three-year anniversary are Vanguard and Global Equity Income, Vanguard Global Emerging Markets, Vanguard Global Balanced.
The mandates to manage those funds are held by, among others, Baillie Gifford and Wellington.
In total, Baillie Gifford, via the global alpha team headed by fund manager Charles Plowden and the emerging markets team and others, manage about £28bn in total for Vanguard clients.
Wellington is an institutional-only fund manager and was the first firm to hire Jack Bogle, who went on to found Vanguard and passed away in January.
Mr Surrey said Vanguard meet about 200 active fund managers a year, but choose less than half a dozen to work with.
Paul Stocks, financial services director at Dobson & Hodge in Doncaster, said: “For the typical client we tend to buy the funds and let the fund manager worry about whether to be in value or growth or any other style at a particular time.
"We are not trying to predict the future. For clients who maybe have a higher risk profile, we might then choose funds based on investment style as they have greater capacity to diversify."