In investing as in most of life, it is human nature to worry about the future. Public pensions have long been an antidote to worry, providing teachers, firefighters, police officers and other public servants with assurance that they will have a modest but secure stream of income during retirement. After all, they are called defined benefit plans precisely because the amount they pay future retirees is predictable.

Investment returns, of course, have ups and downs. But public pensions are the quintessential long-term investment. Quarterly, half-yearly, and even annual results fluctuate, but what matters is the long-term trend over 20, 25, or even 30 years. And that trend is positive for public pension funds, the vast majority of which have patiently weathered every conceivable economic event and continued to meet their obligations.

Indeed, there is ample data to demonstrate that public pension fund investment returns over longer periods meet or exceed the assumed rates used by most plans. For example, the 30-year rolling average return, adjusted by plan size, has been consistently about 9% for each year since 2000, a period that included the deep recession of 2007 to 2009…