When you hear statistics in the news - on monthly employment, consumer spending, or GDP growth - these statistics have been aggregated from survey data of persons, families, and businesses. When you read statistics about the population of the United States and its demographic characteristics, this has been aggregated from the decennial Census of hundreds of millions of Americans. Microdata refers to data at its most basic level, the individual unit. For researchers, the availability of microdata allows them to download it into statistical software and do their own analyses. With the advent of the Internet and ever greater computing power, microdata is becoming widely available. Microdata is becoming an information resource in much the same way that textual sources already are.
The purpose of this guide is to provide access to readily available microdata that require minimal registration, pre-approval, or special handling. With a lot of data collected, there are major privacy concerns regarding financial, medical, or personal information. Most of the data sources in this guide are "anonomized", that is, stripped of any information leading back to specific persons or businesses.