The New York Times, say, reaches far more readers than ever online. But of its 17 million unique visitors a month (in the US, where it’s far easier and more lucrative for the paper to sell ads), a sizable chunk click one story via Twitter or HuffPo or some such site and don’t return. The truly valuable digital readers are a core of about 5 to 10 percent who are heavy users of nytimes.com or its apps. Those readers spend many hours a month reading the NYT online. The 700,000 who pay an average $202 a year to do so are what you might call the super-valuable online readers.