Calpers, the largest state pension in the U.S., saw its funding level rise 7 percentage points last year.

The $300 billion-plus pension fund racked up an 18.4 percent gain on its investments in 2014, giving it a funding level of 77 percent at year-end. That's up from 70 percent in 2013. 

Pensions across the U.S. are short more than an estimated $915 billion needed to cover benefits promised to government workers, according to the Pew Charitable Trust. Taxpayers have been asked to make up the shortfall. A report issued by the California Public Employees' Retirement System said that the return far outpaced the goal of 7.5 percent that had been set by its board. In addition, it's close to double the average annual rate of return for the last three years — which was still double-digit, at 10.4 percent.