"The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor."
What Campbell also states in this principle is that "achievement tests may well be valuable indicators of general school achievement under conditions of normal teaching aimed at general competence. But when test scores become the goal of the teaching process, they both lose their value as indicators of educational status and distort the educational process in undesirable ways. (Similar biases of course surround the use of objective tests in courses or as entrance examinations.)"
Campbell's law was published in 1976 by Donald T. Campbell, a social psychologist, an experimental social science researcher and the author of many works on research methodology. Closely related ideas are known under different names, e.g. Goodhart's law, and the Lucas critique. Another concept related to Campbell's law emerged in 2006 when UK researchers Rebecca Boden and Debbie Epstein published an analysis of evidence-based policy, a practice espoused by Prime Minister Tony Blair. In the paper, Boden and Epstein described how a government that tries to base its policy on evidence can actually end up producing corrupted data because it, "seeks to capture and control the knowledge producing processes to the point where this type of ‘research’ might best be described as ‘policy-based evidence’." (Boden and Epstein 2006: 226)
See also 
- Campbell, Donald T., Assessing the Impact of Planned Social Change The Public Affairs Center, Dartmouth College, Hanover New Hampshire, USA. December, 1976.
- Managing the Research Imagination? Globalisation and Research in Higher Education. Globalisation, Societies and Education
- Rothstein, Jesse (University of California - Berkeley) "Review of Learning About Teaching" National Education Policy Center, 1/13/11. http://nepc.colorado.edu/thinktank/review-learning-about-teaching
- "Learning About Teaching" Bill & Melinda Gates Foundation, 12/10/10. http://www.gatesfoundation.org/college-ready-education/Documents/preliminary-findings-research-paper.pdf
- Berliner, David C. & Nichols, Sharon L. "High-Stakes Testing Is Putting the Nation At Risk" Education Week, 3/12/07. http://www.edweek.org/ew/articles/2007/03/12/27berliner.h26.html
- Nichols, Sharon L. & Berliner, David C. "The Inevitable Corruption of Indicators and Educators Through High-Stakes Testing" The Great Lakes Center for Education Research & Practice, East Lansing, MI, March 2005. http://epsl.asu.edu/epru/documents/EPSL-0503-101-EPRU.pdf
- Nichols, S. L., & Berlner, D. C. (2007). Collateral Damage: How high-stakes testing corrupts America's schools Cambridge, MA: Harvard Education Press
- Tony Waters, "Campbell's law, planned social change, Vietnam war deaths, and condom distributions in refuge camps" at Ethnography.com