AND PEOPLE WONDER WHY WE'RE IN A DEFLATIONARY EPOCH?:

Measuring the economic impact of all the ways the internet has changed people's lives is devilishly difficult because so much of it has no price. It is easier to quantify the losses Wikipedia has inflicted on encyclopedia publishers than the benefits it has generated for users like Ms Mollica. This problem is an old one in economics. GDP measures monetary transactions, not welfare. Consider someone who would pay $50 for the latest Harry Potter novel but only has to pay $20. The $30 difference represents a non-monetary benefit called "consumer surplus". The amount of internet activity that actually shows up in GDP--Google's ad sales, for example--significantly understates its contribution to welfare by excluding the consumer surplus that accrues to Google's users. The hard question to answer is by how much.

Shane Greenstein of Northwestern University and Ryan McDevitt of the University of Rochester calculated the consumer surplus generated by the spread of broadband access (which ought to include the surplus generated by internet services, since that is why consumers pay for broadband). They did so by constructing a demand curve. Say that in 1999 a person pays $20 a month for internet access. By 2006 the spread of broadband has lowered the real price to $17. That subscriber now enjoys consumer surplus of $3 per year, even as the lower price lures more subscribers. The authors reckon that by 2006 broadband was generating $39 billion in revenue and $5 billion-$7 billion in consumer surplus a year. Based on its share of online viewing, Mr Greenstein thinks Wikipedia accounted for up to $50m of that surplus.

Such numbers probably understate things. The authors' calculations assume internet access meant the same thing in 2006 as it did in 1999. But the advent of new services such as Google and Facebook meant internet access in 2006 was worth much more than in 1999. So the surplus would have been bigger, too.

More important, consumers may not incorporate the value of free internet services when deciding what to pay for internet access. Another approach is simply to ask consumers what they would pay if they had to. In a study commissioned by IAB Europe, a web-advertising industry group, McKinsey, a consultancy, asked 3,360 consumers in six countries what they would pay for 16 internet services that are now largely financed by ads. On average, households would pay €38 ($50) a month each for services they now get free. After subtracting the costs associated with intrusive ads and forgone privacy, McKinsey reckoned free ad-supported internet services generated €32 billion of consumer surplus in America and €69 billion in Europe. E-mail accounted for 16% of the total surplus across America and Europe, search 15% and social networks 11%.

Another way to infer consumer surplus is from the time saved using the internet. In a paper partly funded by Google, Yan Chen, Grace YoungJoo Jeon and Yong-Mi Kim, all of the University of Michigan, asked a team of researchers to answer questions culled from web searches. The questions included teasers like: "In making cookies, does the use of butter or margarine affect the size of the cookie?" On average, it took participants seven minutes to answer the questions using a search engine, and 22 minutes using the University of Michigan's library. Hal Varian, Google's chief economist, then calculated that those savings worked out to 3.75 minutes per day for the typical user. Assigning that time a value of $22 per hour (the average wage in America), he reckons search generates $500 of consumer surplus per user annually, or $65 billion-$150 billion nationally.

Yet another technique is to assign a value to the leisure time spent on the web.

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