Approximately $13.2 billion flowed into exchange-traded products in July, according to statistics compiled electronically by National Stock Exchange.

That brings assets in U.S.-listed Exchange-Traded Funds (ETF) and Exchange-Traded Notes (ETN) to $1.107 trillion. Thaat is an increase of roughly 33% from a year ago, when assets totaled $835 billion at the end of July. 

The number of listed products now is 1,295 compared to 1,032 last year.

The $13.2 billion amounts to 18.6% of the total of $71.1 billion that has come into exchange-traded products through the first seven months of the year.

ETF/ETN notional trading volume during July 2011 totaled approximately $1.5 trillion, representing almost 31% of all U.S. equity trading volume, NSX said.

BlackRock remained the largest manager of exchange-traded products, with $473.3 billion under management in various forms.