Assets in exchange-traded funds increased $4 billion in November, according to the Investment Company Institute.

The combined assets of the nation’s 920 ETFs were $927.62 billion in November, according to ICI.

That compared to $923.5 billion at the end of October 2010 and $737.9 billion at the end of November 2009. 

But growth in exchange-traded funds, which are like mutual fund companies' index funds but are traded on exchanges throughout the day, has slowed down.

For the 11 months ended November 30, 2010, the amount of assets held in ETFs grew 19.4%, from $771.1 billion to $927.6 billion.

For the 11 months ended December 31, 2009, the assets grew from $495.4 billion to $777.1 billion.

That means that ETFs added $281.7 billion of investor money in the last 11 months of 2009 and only $150.5 billion in the first 11 months of 2010.