According to the Investment Company Institute, or ICI, the combined assets of U.S. ETFs increased by $36.30 billion to $608.42 billion in December.

The latest asset figures represent a 6.3 percent decrease compared to November, but the year-over-year numbers still show surging ETF assets. Since December 2006, ETF assets have jumped by 44 percent or by $185.87 billion. During December, the value of all ETF shares issued exceeded that of shares redeemed by $44.52 billion.

ICI is a national association of U.S. registered investment companies.

Ron DeLegge is the San Diego-based editor of www.etfguide.com.