Did you know?
Copyright law does not apply to facts, data, or ideas. But it does apply to their arrangement (as in a data base). But, just because data is not protected by copyright, it does not mean there are not other legal considerations.
The most common is privacy. Research in medicine, sociology, education, and public policy may include information about individuals that is protected either by federal privacy legislation or by commitments made by the researchers who collected it. Attempts to anonymize data before sharing it do not ensure that individual research subjects will not be identifiable, thus compromising privacy. For more information, check out Facts and Data from the University of Michigan.
Why can't I find anything more recent?
Data can be expensive and time-consuming to produce and process - often depending on its size, scope, complexity, and available funding. The more people a survey incledes, or the more observations that are recorded, the longer it will take for the data to be collected and processed, and the more expensive it is.
Data can also be embargoed. This is a ban on the publication of documents (or in this case) data, for security or copyright reasons. Scientists can wait until they have finished analyzing their data before making it available. The US Census does this as well. Reports by the Census on the changes in the population were available before the data was released to the general public.