A head’s up to those who invest their money with Vanguard of Malvern – and there must be many of you since the company says it manages $2 trillion in assets.

The company has issued revised prospectuses on about 80 different funds, and the expense ratios (operating costs) of some of those funds have changed. This will mean higher operating costs to some investors, lower costs for some, and no change for others.

The less you pay to invest, the more you keep in your pocket. Vanguard reports in 2013, the average expense ratio of its mutual funds was 0.19 percent, lower than the industry average of 1.08 percent.

Each percentage point in an expense ratio represents an annual charge of $100 against every $10,000 you invest in that fund. In other words, if you have $10,000 in a hypothetical fund with a 0.50 percent expense ratio, you’re charged $50 each year. So, a 0.15 percent expense reduction would save you $15, while a 0.15 percent increase would cost you an extra $15.

Vanguard, founded in 1975, has historically focused on keeping operating costs low. Since investment costs have a major effect on net returns it’s important to pay attention to them, as seemingly minor differences in expense ratios can add up significantly over time. (Expense ratios are the portion of a mutual fund’s operating expenses passed on to shareholders, shown as a percentage of the fund’s total assets.)

In announcing the changes, Vanguard is advising investors a change in a fund’s expense ratio should not be the only reason to buy or sell shares. Vanguard advises considering your personal financial goals, your time frame and your tolerance for bearing the risks of investing – as well as tax implications.

Also, Vanguard advises that buying a fund solely based on past performance can turn into a costly mistake outweighing the considerable benefits of a low expense ratio. A full explanation with a table listing changes to all funds is here.