The fund’s popularity has soared in recent years, as has "passive" investment more generally. Passive funds are typically much cheaper than traditional funds, as there is no need to pay a professional to manage your money. For instance, a tracker fund might charge 0.25pc where an "active" fund might charge 1.7pc. In the case of Vanguard Total Stock Market Index fund, investors need to pay only 0.17pc a year.