This excerpt taken from the NDAQ 10-Q filed Nov 7, 2008.
U.S. Listing Revenues
Listing Services revenues in the U.S. include fees for annual renewals, listing of additional shares fees and initial listing fees for companies listed on The NASDAQ Stock Market. For our U.S. operations, fees are generally calculated based upon total shares outstanding for the issuing company. These fees are initially deferred and amortized over the estimated periods for which the services are provided. Revenues from annual renewal fees are amortized on a pro-rata basis over the calendar year and listing of additional shares fees and initial listing fees are amortized over four and six years, respectively.
Annual renewal fees decreased in the third quarter and first nine months of 2008 compared with the same periods in 2007. The number of companies listed on The NASDAQ Stock Market on January 1, 2008 was 3,135, compared to 3,193 on January 1, 2007, the date on which listed companies are billed their annual fees. The decrease in the number of listed companies was due to 348 delistings by Nasdaq during 2007, partially offset by 290 new listings during 2007. The number of listed companies as of January 1, 2008 and 2007 also includes separately listed ETFs.