In Pittsburgh, where steel maker Andrew Carnegie turned his fortune to building libraries both across the country and in his adopted hometown, where the playwright August Wilson took to the books after he did not take to school, the benefits of community libraries might seem clear enough without documenting the obvious.

But that is what Carnegie Library of Pittsburgh recently did with a study of its impact. It turns out to have been a good exercise -- and, far from just telling us what we know, provided some surprises.

Andrew Carnegie, ever oriented toward the bottom line, would surely have approved this business-like approach. The Carnegie Mellon University Center for Economic Development conducted the study, which was released three weeks ago. It documents an impressive array of benefits flowing from the Carnegie Library of Pittsburgh, which has 19 neighborhood locations in the city, including the main library in Oakland.

According to the study, which surveyed 1,300 individuals and interviewed several focus groups, the Carnegie Library sustains 726 jobs and more than $63 million in economic output in Allegheny County annually. For every dollar the city of Pittsburgh and the Allegheny County Regional Asset District provide the Carnegie Library, the study contends that the library provides more than $6 worth of benefits.

But the study does more than put the library's value in dollars and cents -- it provides valuable insights into the continuing power of libraries in the Internet age. As it turns out, books and the Internet appear to complement each other in a library setting. The study found that while the majority of visitors borrow materials including books, videos or CDs, many come to use computers -- 63 percent of survey respondents said that the availability of computers was a major benefit.

And who knew this? The survey found that the Carnegie Library of Pittsburgh is the area's most visited regional asset -- more people visit the library in a year than patronize any Pittsburgh sports team in a season. More than half of the city's residents and nearly one out of five residents of the county have a Carnegie Library of Pittsburgh card. And many of the library users are young.

All these are arguments that help the cause of the Carnegie Library system, which depends on its RAD funding not being eroded and is in the midst of a $55 million capital campaign. But by extension, these insights make a key point about the value of the more than 80 libraries in Allegheny County.

Libraries are a good investment. As it happens, Gov. Ed Rendell's budget would restore library funding across the state to the level of 2002, when cutbacks in state support led to reduced hours. For the Carnegie Library of Pittsburgh, passing this proposal would add about $500,000 to its state funding. It's time to stop beggaring libraries, one of our great, unsung community assets.