A 1988 paper, Test of a Field Model of Consciousness and Social Change: The Transcendental Meditation and TM-Sidhi Program and Decreased Urban Crime describes some studies of data from the '70s and found that the more people who attended group practice of Transcendental Meditation, the more violent crime was decreased in the District of Columbia. They describe this as evidence of a causal relationship.
A 1999 paper, Effects of Group Practice of the Transcendental Meditation Program on Preventing Violent Crime in Washington, D.C.: Results of the National Demonstration Project, June--July 1993 describe a prospective experiment in 1993, where 4,000 people participated in Transcendental Meditation, and they found a 15.6% reduction in violent crimes in D.C., after controlling for temperature.
The claim that personal meditation is capable of "increasing coherence and reducing stress in the collective consciousness of the District" and thus decrease crime is extraordinary and incredibly important, if true.
Is there a causal relationship between Transcendental Meditation and lower violent crime rates across a city (beyond the participants themselves)?