This tends to move with interest rates, even though it is not a fixed rate bond portfolio. When the Fed has been buying bonds and driving down long term treasury rates to below 2%, this rallied into the $120s. Once the Fed started talking about tapering its bond purchases (causing long term interest rates to go up), this security has dropped 10%.
So, what would drive the price up again is lower interest rates, which would likely happen now if the economic numbers start looking weak again. Weak numbers might change the Feds tapering plans and long term rates might go back down again.
It doesn't seem too likely at the moment for this to go back to $118. The bond rates below 2% were an abberation, and not that likely to return under normal economic conditions. If you think rates are going up even further, then this is not the best thing to hold.
From a technical standpoint the price should catch at around $105; let's hope it holds there. I sold earlier @ $118 (thanks ;) to lock in a profit and make a house downpayment, then got back in @ $113 thinking that it had found a bottom. If you were hoping to make a quick profit then get out now. If like most of us, you got in with a fraction of your total investment resources as a hedge against unforeseen, future inflation then put it in your back pocket, be glad you're at least getting a dividend, and be even more glad when inflation soars after the US attacks Syria and the Chinese not only refuse to buy any more treasuries but start selling the ones they have, leading to a collapse of the dollar. Or something like that....
Well, there is an outside chance you could get high CPI numbers and the Fed could cap the yields of government bonds based on some yet unknown emergency. The Fed capped the 10 year treasury at 2.5% during and after WW2. During the late 1940's there was one year with an annual 20% CPI rate to go along with the 2.5% cap.
I am not saying this will happen again, but it could rhyme. It seems inconceivable that the CPI could get that high as it has become so much gov't. controlled nonsense these days, but if the US dollar is threatened, you could get higher inflation than we have known recently. TIPS is a "safe" play on dollar erosion, ultimately. You just need a little faster erosion :)