再Internet benefits, March 9th 2013 P72 インターネットの賜物
When her two-year-old daughter was diagnosed with cancer in 1992, Judy Mollica spent hours in a nearby medical library in South Florida, combing through journals for information about her child's condition. Upon seeing an unfamiliar term she would stop and hunt down its meaning elsewhere in the library. It was, she says, like ゛walking in the dark゛. Her daughter recovered but in 2005 was diagnosed with a different form of cancer. This time, Ms Mollica was able to stay by her side. She could read articles online, instantly look up medical and scientific terms on Wikipedia, and then follow footnotes to new sources. She could converse with her daughter's specialists like a fellow doctor. Wikipedia, she says, not only saved her time but gave her a greater sense of control. ゛You can't put a price on that.゛ 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 accues to Google's users. The hard question to answer is by how much. (中略) Another way to infer consumer surplus is from the time saved using the internet. In a paper partly funded 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. Assingning 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. Erik Brynjolfsson and Joo Hee Oh of the Massachusetts Institute of Technology note that between 2002 and 2011, the amount of leisure time Americans spent on the internet rose from 3 to 5.8 hours per week. The authors conclude that in so far as consumers must have valued their time on the internet more than the alternatives, this increase must reflect a growing consumer surplus from the internet, which they value at $564 billion in 2011, or $2,600 per user. Had this growth in surplus been included in GDP, it would have raised economic growth since 2002 by 0.39 percentage points on average. These are impressive figures, but they also merit scepticism. Would consumers really pay $2,600 for the internet? Shouldn't other free leisure activities, such as watching television or - heaven forbid - playing with your children have just as much value? And in other ways the subtracts value：the productivity destroyed by incessant checking of Twitter, the human interactions replacee by e-mail. Ms Mollica says people in hospital waiting rooms used to develop a camaraderie rooted in their shared experiences. ゛But now everyone stares into their phone because they're texting or e-mailing.゛
