Historically, data sources for urban planning have remained relatively stable. Planners relied on a collection of well-known government-produced datasets to do their work, including statistics and geographic layers from federal, state and local sources. Produced by regulatory processes or occasional surveys, the strengths and limitations of these sources are well known to planners and many citizens. However all this is beginning to change. Not only has the U.S. Census Bureau's American Community Survey introduced a bewildering variety of data products, all with margins of error, three interrelated categories of new data are growing rapidly: crowdsourced, private, and "big" data.