From Yifan Cao and Adam Shapiro at the Federal Reserve Bank of San Francisco:
The well-known Phillips curve suggests that future inflation depends on current and past inflation and a measure of economic slack or resource utilization. Using the unemployment gap to measure slack, a simple Phillips curve currently predicts that inflation will remain quite low through 2015. Two variations of the model, which impose a higher anchor for inflation expectations or focus only on a short-term unemployment gap, still predict that inflation will remain low, albeit higher than implied by the basic model.
Read more at Federal Reserve Bank San Francisco | Will Inflation Remain Low?.