Total assets under management in U.S. exchange traded funds are up by $115 billion so far this year thanks to inflows and market appreciation.

“ETF fund flows have been a uniformly positive source of capital into U.S. risk markets in 2012: $39 billion of new cash overall,” says Nicholas Colas, ConvergEx Group chief market strategist. [Bond ETF Assets Rise Nearly 40% in a Year]

In 2012, investors have pumped $20 billion into stock ETFs, $13 billion into bond funds and $5 billion into commodity portfolios. [ETFs Gathering Record Inflows in 2012]

The top-selling funds this year are iShares iBoxx High Yield Corporate Bond (NYSEArca: HYG), SPDR Barclays High Yield Bond (NYSEArca: JNK), iShares iBoxx $ Investment Grade corporate Bond Fund (NYSEArca: LQD), Vanguard MSCI Emerging Markets ETF (NYSEArca: VWO), iPath S&P 500 VIX Short Term Futures ETN (NYSEArca: VXX) and SPDR Gold Shares (NYSEArca: GLD). [Why Trading in VIX ETFs is Surging]

Assets in exchange traded funds and notes total about $1.2 trillion. [ETF Spotlight: Vanguard Emerging Markets]

“Total AUM is actually up $115 billion with the generally positive performance of capital markets,” Colas wrote in a note Friday.

“ETFs have been the most constant source of new money – notably into U.S. stocks – for several years, especially as compared to mutual funds. Consider that thus far in 2012, mutual fund managers have seen $22 billion in outflows from domestic equity mutual fund products, only partially offset by $4 billion of fresh capital into foreign equity funds,” the strategist added. “Compare that with the $20 billion of new money into equity ETFs thus far for 2012, and it is easy to see that ETFs are adding to available capital at a faster rate than mutual funds are shrinking that same pool of money.”

Full disclosure: Tom Lydon’s clients own GLD and VWO.