According to this New York Post story(free registration required), the New York Times is losing 20% of it’s local market in the boroughs between 2001 and 2004.
Since the mid-1990s, the Times has embarked on a strategy to expand nationally to reduce its dependence on the New York ad market while going head-to-head with other national papers, including The Wall Street Journal and USA Today.
As part of that plan, the Times targeted national advertisers and eventually stopped breaking out numbers for circulation within the city.