While still expanding over the last year, the exchange traded fund universe has shrunk in May as the heightened uncertainty pushed investors away from stock ETFs, and the influx of cash into safe-haven bonds was not enough to offset the total losses.

According to an Investment Company Institute research note, total ETF assets as of May stood at $1.115 trillion, down from $1.186 trillion in April but still higher than the $1.087 trillion in May 2011. [ETF Growth May Cool: Bernstein]

Assets in domestic equity ETFs fell to $650.8 billion in May from $696.6 billion in April and global/international equity ETFs shrunk to $247.9 billion from $280.9 billion. Meanwhile, bond ETF assets grew to $216.4 billion in May from $209 billion in the previous month.

There were 1,212 ETF products available as of May. Domestic equity ETFs still dominated the space, with 597 products, followed by 404 global/international equity ETFs and 201 bond ETFs.

It is also interesting to note that ETF activity is rising. Specifically, gross issuances rose to $104.1 billion in May from $82 billion in April, and gross redemptions increased to $101.4 billion from $79.5 billion. Additionally, total ETF shares issued exceed those redeemed by $2.72 billion in May, whereas ETF shares redeemed exceeded those issued by $3.65 billion in the same month last year.

For more information on ETF asset flows, visit our ETF performance category.

Max Chen contributed to this article.

The opinions and forecasts expressed herein are solely those of Tom Lydon, and may not actually come to pass. Information on this site should not be used or construed as an offer to sell, a solicitation of an offer to buy, or a recommendation for any product.