This document discusses various concepts for measuring the economic value of public libraries, which provide both tangible and intangible benefits. It outlines that economic benefit looks at the overall value to society, while economic impact examines net changes to the local economy. Non-market goods and services provided by libraries are difficult to quantify but important to include. The document also reviews methods like cost-benefit analysis, return on investment calculations, contingent valuation surveys, and the need to incorporate both quantitative and qualitative data to fully account for libraries' complex role.