Expense ratios fell on 11 target-date funds from Vanguard. (Photo: AP)

Vanguard said Monday that 18 of 28 funds had slightly lower expense ratios, according to the latest reports shared with investors this month. Of the other 10 funds, the fees of eight remained unchanged, while two had small increases.

(The popular fund family released the figures for Admiral and Investor shares, as well as for Institutional and Institutional Plus shares.)

For instance, 11 target-date retirement funds (2010-2055) had a 0.01% decrease in expenses. The fee ratio on the Target Retirement 2030 Fund dropped from 0.18% to 0.17%.

Two funds experienced an increase of 0.01%: Growth and Income Fund, both Admiral and Investor shares, and the Growth Equity Fund’s Investor shares.

Each percentage point in an expense ratio represents an annual charge of $100 against every $10,000 invested, according to the fund giant. Thus, a fund with a 0.17% expense ratio charges its shareholders $17 for every $10,000 invested, and a reduction from 0.18% to 0.17% means a savings of $1 for every $10,000 invested.

“A fund’s expense ratio may change from year to year in response to changes in its assets and/or changes in the cost of managing it,” Vanguard said in an online report. “For example, economies of scale resulting from an increase in assets due to market appreciation or investor cash flow can result in a reduction, while a decline in assets can cause the expense ratio to rise.”

Vanguard says that because its corporate entity is owned by the funds themselves (rather than any private or public interests), it has been able to reduce its funds’ average expense ratio by more than 77%—from 0.89% in 1975 to 0.20% as of Dec. 31, 2011.

According to Morningstar’s latest estimates, Vanguard continues to dominate the open-end mutual fund industry. It had $1.6 trillion in open-fund assets as of Dec. 31, 2012, representing a nearly 17% market share. Its 2012 inflows totaled $86.1 billion.

Still, PIMCO had flows of $62.7 billion in 2012, including inflows of $5.3 billion in December—when Vanguard had $55 million of net outflows. PIMCO has a roughly 6% overall market share of the open-fund marketplace with $563 billion in assets.