But what are these averages to you? just because you own a fund whose share value increased 8 percent doesn’t mean that your own investment earned the same amount. To find your personal return, you have to account for other factors, including when you bought your shares and whether you paid a sales load. If you don’t know how to make these adjustments, you’re probably overestimating how much your nest egg has actually earned.

Take the question of timing. Your fund’s official performance results assume a fixed investment, with dividends used to buy more shares. But that doesn’t describe the way most investors handle their money. You might buy shares monthly, through a 401(k) retirement plan; or add cash occasionally, when a big check comes in; or sell some shares, or use your dividends to live on. These choices modify your gains. The average equity-income fund rose more than 11 percent this year so far, with dividends reinvested, but only about 9 percent with dividends cashed out

You can figure your true return if you’re quick with spreadsheets or a financial calculator. But you shouldn’t have to bother. Your mutual fund should compute it for you, showing you both the fund’s return and your own personal gain or loss.

To most funds, this suggestion is as welcome as a squirt in the eye. “A logistical nightmare,” objects Malin Jennings of the Investment Company Institute. But individualized returns are commonplace at other firms. They’re provided by investment advisers who run individual portfolios, and by many of the financial planners who put clients’ money into mutual funds. Funds could offer this service themselves, if they built up a database, adopted certain accounting conventions and developed software (not a big deal).

Many industry honchos argue that investors don’t need their actual financial results. Even Vanguard Group chairman John Bogle, normally a voice for disclosure, doesn’t think much of personalized statements. “What would you do with them?” he asks. Well, you might change your investment approach, if you saw you were earning less than you thought. You might try harder to leave your retirement fund intact. Above all, you would know the truth. In the words of the late, great physicist, Richard Fevnman, “The first principle is that you must not fool yourself and you are the easiest person to fool.”

As far as I know, only one fund group calculates personal investment results: the 895 billion IDS Financial Services, based in Minneapolis. These statements, available only through the company’s financial planners, disclose the full history of your account: cash in and cash out, current dividend yields and total returns over 1, 5 and 10 years. “This helps demystify how the clients are doing and makes them smarter about investing,” says IDS’s Jeff Hovis, who developed the reports. The system cost $600,000, he says, plus $300,000 a year to run.

Fidelity Investments in Boston may be working on something similar. “We don’t want to tip our hand,” a spokesperson says, “but we’ll soon be addressing these concerns.”

Even riper for a shake-up are bank trust departments, whose client reports have long been known as models of the artful dodge. They typically show, in loving detail, the cost and value of each security, as well as the interest and dividends paid. But they don’t compute the percentage that was earned on capital that year. Nor do they reveal the trust’s total investment return (counting principal and interest), compared with standard market benchmarks. So there’s no way to measure your banker’s skill.

John Lipori, vice president for trusts at the Bank of New York, says that income beneficiaries care only about the size of their checks, not their total return. But if it were me, I’d want to know whether my trust earned 7 percent this year or only 2 percent. If I stood to inherit the principal, I’d want to see whether the capital growth at least matched the inflation rate.

Like it or not, the industry will have to move toward personal performance reports, as clients grow more knowledgeable about their money. Citibank, for one, expects to show total returns on its statements in 1994. “It’s the climate out there,” says Isabel Miranda-Mazzucca, Citibank’s vice president for trusts. “To attract clients, you have to show results.”

The last and toughest nut to crack is the statement sent by your stockbroker. It’s a scandal; a disgrace. Your securities are listed, your income shown and all transactions noted. But you don’t see the total commissions paid or your gross returns, so there’s no way to calculate how well you or your broker have performed.

That’s no accident, of course. “If brokers started showing performance, investors may see they could be doing better with a mutual fund,” says securities arbitration specialist Mary Calhoun of Watertown, Mass. Even Merrill Lynch’s fancy statement for upscale clients glides by the question of how well each investor actually did. Merrill’s John Galvin says he’s working on a performance measure, which will be ready in a couple of years.

Two other items reduce your returns from the averages shown in newspaper reports. You earn comparatively less from a fund that charges an upfront sales load. And your profits are always reduced by taxes. For a rough idea of what this means, check your newsstand for Fortune’s Investor’s Guide, which shows fund performance adjusted for both taxes and loads.

It does seem clear that disclosure trends are edging in the right direction. But the pace is glacial and no law is likely to come to your rescue. To get results, investors will have to pester their banks, funds and brokers themselves.