Data is not copyrightable in the U.S. (although a specific expression of data, such as a chart or table in a book, may be)
Data can be licensed, and certain licenses may help ensure proper attribution and protect your data in countries where copyright applies. Some data providers use licenses that limit how the data can be used in order to protect the privacy of participants in a study or guide later uses of the data.
If you would like to apply a license to your own data, you are encouraged to make it as open as appropriate so that others can use and build upon your work. To promote sharing and the unlimited use of your data, you can use a CC0 license from Creative Commons that grants the public an "unconditional, irrevocable, non-exclusive, royalty free license to use the work for any purpose."
Do note that the reuse and licensing of data compiled from other sources (not your own) is subject to the conditions set forth by the authors of that data. Federal and government data sources usually impose few conditions. Researchers, on the other hand, may impose strict requirements in certain situations. It is important to know when and under what circumstances you may use and share data created by others.
Per the WUSTL Intellectual Property Policy, all intellectual property, including data, is owned by the University if significant University resources were used or if it is created pursuant to a research project funded through corporate, federal or other external sponsors administered by the University.
However, the principal investigator typically retains the rights and responsibilities over control and licensing of data and related materials.
Maintaining the confidentiality of research subjects is of the utmost importance for ethical reasons, and to ensure the continuing willingness of subjects to particiate in research. Therefore, researchers should balance the conflict that may arise between ethical requirements and other requirements for the retention and deposit of data in a repository or archive for purposes of peer review and expanding knowledge.
It is possible to ethically share confidential data. This can be achieved by protecting privacy through anonymising data that would otherwise identify individual research subjects, aggregating data, controlling access to the data through embargoes or access/licensing terms and conditions, or by gaining the informed consent of research participants that includes consent for data sharing.
For more information on the ethical conduct of research at Washington University, please visit the Research Education and Information page of the Office of the Vice Chancellor of Research.