Abstract:Using transportation and other social science data examples, and focusing in depth on telecommuting, we demonstrate that definitions, measurement instruments, sampling and sometimes vested interests affect the quality and utility even of seemingly objective and "measurable" data. Little consensus exists with respect to the definition of telecommuting, or to possible distinctions from related terms such as teleworking. Such a consensus is unlikely, since the "best" definition of telecommuting depends on one's point of reference and purpose. However, differing definitions confound efforts to measure the amount of telecommuting and how it is changing over time. This paper evaluates estimates of the amounts of telecommuting occurring in the U. S. obtained from several different sources: the U. S. Census, the American Housing Survey, several Work at Home supplements to the Current Population Survey, a series of market research surveys, and the trade association-sponsored Telework America surveys. Many of the issues raised here are transferable to other contexts, and indirectly serve as suggestions for improving data collection in the future.