September reports for exchange traded funds (ETFs) and exchange traded notes (ETNs) are in, and they are as balanced and crisp as an autumn day.

National Stock Exchange (NSX) announced that U.S.-listed ETF and ETN assets reached $593.3 billion by the end of the month. This is a 5% increase over the total $566.2 billion of 2007, reports MarketWatch. Net cash inflows for the month of September 2008 reached a new total of $57.2 billion.

ETF/ETN notional trading volume during September 2008 totaled $2.8 trillion, representing a record 35% of all U.S. equity trading volume, showing the interest of many investors. The total number of listed products is at 813, versus 593 as of one year ago.

We think it’s just the beginning – the markets aren’t attracting many investors right now, but when they do, look out. ETFs are sure to gobble up a great portion of the assets.