The Oregon Investment Council, which is responsible for investing state pension funds, outperformed all of its peers over the past decade.

The ranking comes from the Wilshire Trust Universe Comparison Service, which compares the performance of large public pension funds.

Over the past decade, Wilshire found that Oregon's primary fund, which now holds assets worth $70.5 billion, earned an average of 5.5 percent annually, better than all of its peers.

"Our goal is exemplary performance over the very long term," Oregon Investment Council Chair Rukaiyah Adams said in a statement.

"Strong investment performance is good news for every Oregonian," added State Treasurer Tobias Read, who is a member of the investment Council. "Every dollar earned from investment returns is a dollar that doesn't need to come from the budget."

That's the good news.

The bad news is that the OIC's benchmark, a measurement called "the average assumed rate," is 7.5 percent.

Think of that rate as fund's break-even number: if investments return less than 7.5 percent, as they have for the past decade, the fund's deficit increases because the state's obligation to retirees is growing faster than investment returns.

That's a big part of why the unfunded Public Employee Retirement System liability has grown from about $1.5 billion in 2007 to about $22 billion today.