My co-blogger Jonathan Adler notes the Wall Street Journal essay reporting the following about blogging:

The best studies we can find say we are a nation of over 20 million bloggers, with 1.7 million profiting from the work, and 452,000 of those using blogging as their primary source of income. That's almost 2 million Americans getting paid by the word, the post, or the click — whether on their site or someone else's. And that's nearly half a million of whom it can be said, as Bob Dylan did of Hurricane Carter: "It's my work he'd say, I do it for pay."

The idea that there are 452,000 people in the United States using blogging as their primary source of income seems truly incredible to me. The Volokh Conspiracy is a pretty popular blog, but we tend to earn less than minimum wage for our time blogging here.

   If I'm not mistaken, the 452,000 figure is way off. The conclusion that 452,000 people in the United States use blogging as their primary source of income is based on calculations from a blog post at Media Bistro that links to a report by Technorati on the state of the blogophere. The Media Bistro post copies a chart from the Technorati report (see it here) in which two percent of the participating bloggers reported that blogging was their primary source of income.

  The trick, though, is that Technorati's participating bloggers were likely an unusual bunch rather than a representative one. According to the report's explanation of its methodology:

We emailed a survey invitation to a random sample of Technorati registered users around the world. To qualify for the survey, respondents needed to be bloggers over 18 years old. The survey was hosted by Decipher Inc., was in the field from July 28, 2008 through August 4, 2008, and received 1,290 completed responses from 66 countries.

The methodology doesn't tell us how many e-mails were sent out to get those 1,290 responses, or how many of those responses were from bloggers in the United States. Nor do we know if Technorati's e-mail asking for responses promised respondents anything in the nature of free advertising for their blogs (some was given, in the form of individual blogger profiles in the report) which would likely skew the numbers. All we know is that Technorati received 1,290 responses from bloggers who responded to its query. Of the ones who responded from around the world, 2% — about 25 people — said that they relied on blogging as their primary source of income.

  It seems that the WSJ story assumed that this group of bloggers was representative of the bloggers in the United States. The WSJ article thus calculated the number of bloggers making their primary living from blogging by taking one figure they had — that there were 22.6 million bloggers in the U.S. in 2007 — and then multiplying by the percentage of bloggers in the Technorati study who said that blogging was their primary source of income — that is, two percent. Voila, 22.6 million times .02 = 452,6000 people in the U.S. making their primary living from blogging. But the group of bloggers who are enthusiastic enough about blogging and eager enough to take their time to complete a survey is likely highly unrepresentative of the whole.