In what may look like a brave switcheroo, the Public Employees Retirement Board on Friday lowered its projected rate of return. The board formally voted that the projected rate of return on investments for the state workers’ retirement plan should be 7.75 percent, down from 8 percent.

It may be a more accurate bet than 8 percent, but make no mistake. This is just another wheeze in the perpetuation of a flawed retirement system.

One way of looking at the PERS system is as a roughly $61 billion promise to pay out future retirement benefits. The fund has been about $14 billion short of having enough to do so.

The money to pay for that promise comes from two places — earnings on investments and the employer contributions from schools and local and state governments. If investment earnings aren’t enough, employer contributions have to make up for it.

The “assumed rate of return” number, then, is one of the most important assumptions in calculating how well Oregon will be able to pay off the promise. It also helps determine the benefits PERS pays out for earlier PERS members.

The Legislature saw fit in 1975 to ensure early PERS members would get favorable investment returns by giving them a guaranteed rate of return. The accounts could never fall below this “assumed rate of return” set by the PERS board.

In other words, benefits wouldn’t fluctuate like a 401(k), according to actual earnings. There was a guarantee. It was one of the low points of the system’s evolution.

The PERS Board reviews and adopts the assumed rate every two years. The board looks at what has happened and tries to project what will happen.

Since the 1970s, the assumed rate of return has changed in only one direction — up. It was 5 percent in 1971 and climbed. Since 1989, it has been at 8 percent.

When you look back far enough, the PERS fund has been doing very well in earning returns. Over the past 20 years, its average earnings have been about 10 percent. That’s about the same as the 25-year average for the S&P 500.

But in recent years, the bond market and the stock market have been much more volatile. For instance, if you look at the S&P 500 average return for five years, it’s only 1.66 percent.

How can the PERS board be expected to guess right? It can’t. If it were really good at guessing, it wouldn’t have a multibillion-dollar shortfall.

So should we all leap to congratulate the board at going from 8 to 7.75? Far from it. If there is any hope of improving the situation with the PERS system, it didn’t happen at the PERS board meeting on Friday. It may only happen through the action of the Legislature, the courts, or an investment market that flies through the roof.