Across several centuries of testing, the predictions of astrology have never been more accurate than that expected by chance alone. One approach used in testing astrology quantitatively is through blind experiment. When specific predictions from astrologers were tested in rigorous experimental procedures in the Carlson test, the predictions were falsified.
The Shawn Carlson‘s double-blind chart matching tests, in which 28 astrologers agreed to match over 100 natal charts to psychological profiles generated by the California Psychological Inventory (CPI) test, is one of the most renowned tests of astrology. The experimental protocol used in Carlson’s study was agreed to by a group of physicists and astrologers prior to the actual experiment itself. Astrologers, nominated by the National Council for Geocosmic Research, acted as the astrological advisors, and helped to ensure, and agreed, that the test was fair.:117:420 They also chose 26 of the 28 astrologers for the tests (the other 2 being interested astrologers who volunteered afterwards) themselves.:420 The astrologers came from both Europe and the United states.:117 The astrologers helped to draw up the central proposition of natal astrology to be tested.:419 Published in Nature in 1985, the study found that predictions based on natal astrology were no better than chance, and that the testing „clearly refutes the astrological hypothesis“.[76