It's the Japanese debt trap. It's causing our unusually restrained inflation levels for the exact same reason it did with Japan. Too much of our income is going to service debt. It locks down the money that would otherwise be available to spur inflation. Not only is the debt service cost a restraint, but the vast outstanding debt levels also cause conservative behavior in all sorts of ways (whether at the consumer level, or higher up the financial chain). The higher US debt levels go vs income, the more difficult it will become to spur inflation in traditional ways. Ultimately, direct currency debasement will be the sole remaining means, as with the Japanese and Yen.