A low-cost option from Vanguard for emerging market stocks is the top-selling ETF this year with more than $6 billion of inflows despite investors pulling some cash in May’s risk-off pullback.

Vanguard MSCI Emerging Markets (NYSEArca: VWO) has attracted $6.4 billion year to date although the ETF saw redemptions of $622 million last month, according to ETF Industry Association data.

The fund has seen much higher inflows in 2012 than competitor iShares MSCI Emerging Markets (NYSEArca: EEM), which tracks the same index.

VWO has lower fees with an expense ratio of 0.20%, versus 0.67% for EEM. [Investors Pull Over $2 Billion from Largest Emerging Market ETFs]

Europe’s debt crisis and weak sentiment have driven strong sales in bond ETFs as investors remain nervous about stocks. Corporate bond funds have been popular with income-seeking investors.

Four of the top 10 asset-gathering exchange traded products in 2012 offer exposure to fixed-income markets, according to BlackRock, which manages the iShares ETFs.

“Vanguard has the highest number of top asset gathering ETPs with six of the top ten. iShares has two,” the firm said in a research note released this week. [Vanguard Leading 2012 ETF Flows]

Top 10 U.S. ETPs Ranked by 2012 Net Inflows

  • Vanguard MSCI Emerging Markets — $6.4 billion
  • iShares iBoxx Investment Grade Corporate Bond Fund (NYSEArca: LQD) — $3.6 billion
  • iShares iBoxx High Yield Corporate Bond Fund (NYSEArca: HYG) — $3.5 billion
  • Vanguard Total Bond Market ETF (NYSEArca: BND) — $2.3 billion
  • Vanguard REIT ETF (NYSEArca: VNQ) — $2 billion
  • Vanguard S&P 500 ETF (NYSEArca: VOO) — $2 billion
  • Vanguard Dividend Appreciation (NYSEArca: VIG) — $1.8 billion
  • SPDR Barclays High Yield Bond (NYSEArca: JNK) — $1.6 billion
  • Vanguard MSCI EAFE (NYSEArca: VEA) — $1.6 billion
  • iPath S&P 500 VIX Short Term Futures ETN (NYSEArca: VXX) — $1.5 billion

Data source: BlackRock