In addition, advances in technology and architecture for linking data systems allow for the integration or linkage of a large number of datasets on different platforms. Information technology systems in the future will increasingly separate the data elements from the business rules for combining the data elements; this will allow for more uses of the data elements and less recoding or reliance on one or more software packages.


Both aggregation and linkage can serve a range of state and local purposes. While both strategies can be utilized for the same datasets, aggregation alone is most common because it offers fewer challenges; the technology, expertise, confidentiality, and security issues are relatively simple. There is increasing interest in linked datasets given the expanded analyses they enable, but for some jurisdictions the expense, privacy obstacles, or other implementation issues make this an unreasonable short-term objective.

Aggregated Data Systems

The oldest and easiest method is to aggregate data from multiple datasets of counted events, problems, or traits for a population group defined by residence in a geographic area or some other factor. Population subgroups may be further defined according to age, race, gender, or other data elements included in the datasets. For example, each of several datasets collected by the federal, state, and local government could be aggregated to the same geographic level to provide a more detailed picture of the health of the entire population of children or a subpopulation. Individual identifiers are typically removed before data are shared for aggregation. Many data-holding agencies (e.g., state or local departments of education) are prohibited by state privacy laws from sharing data unless personal identifiers are removed.

Policy and program decisions about children’s health and environments can be enhanced when aggregated data are provided on the web in a user-friendly manner. Massachusetts and Missouri are two examples of states with web-based systems that provide children’s health data from a variety of sources at several levels of geography. Aggregated data can be used to compare a multitude of health characteristics or influences on health for children in one community or across communities. Local and state programs use data such as these to better plan for services and improve programs and policies as well as evaluate programs over time; several states have systems that make aggregate data available on a regular basis. Consistent with the expectation that collection and provision of data are core functions of public health (Institute of Medicine, 1988, 1996, 2001a), public health departments are responsible for the provision of these aggregate-level data on a timely basis.

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