ETFs that track treasuries have risen despite the fact that the global economy has stabilized since 2008 and interest rates have risen (from near 0 to ~1.5%) My (very simplistic) understanding of treasury prices is that as interest rates rise, treasury bond prices decline. If this is the case, what might have contributed to the rise of an ETF like TLT (which tracks treasury prices)?
I'm not sure where you're getting your information. I used Yahoo Finance to plot the price of TLT (your long-term treasury bond ETF) against the yield on 30-year treasury bonds. The two charts are nearly perfect mirror images of each other, showing that as interest rates rise, the price of the bond ETF falls, and vice versa.
So, it looks like it's not the case that treasury prices have risen despite increasing interest rates.