CHADWICK'S MAJOR CONTRIBUTION TO MODREN CRIMINOLOGY CONSISTED OF: (1) AN ECONOMIC-BASED THEORY OF CRIMINAL BEHAVIOR; AND (2) ANALYSIS OF THE DETERRENT EFFECT OF REDUCING THE EXPECTED GAINS FROM CRIME THROUGH INSTITUTIONAL AND ADMINISTRATIVE CHANGE. HE PROFILED THE COMMON THIEF OF HIS DAY (THIS RESEARCH WAS CONDUCTED FROM 1821 TO 1827) AS A MAN IMPATIENT WITH STEADY LABOR, WITH A STRONG APPETITE FOR THE PLEASURES OF EASE; ONE WHO WAS NOT MUCH DETERRED BY THE THREAT OF PUNISHMENT, BUT WHO VALUED HIGHLY THE PROSPECT OF UNINTERRUPTED SUCCESS AT HIS 'CAREER.' CHADWICK CONCLUDED THAT HABITUAL CRIMES AGAINST PROPERTY WERE NEITHER OF NECESSITY NOR OF PASSION BUT OF CALCULATION OF COMPARATIVE PROFIT (BETWEEN CRIME AND AN HONEST TRADE), AND THAT THE KEY TO PREVENTION THEREFORE LAY IN MEASURES TO REDUCE THE PROFITS OF CRIME. THESE MEASURES WERE BASED ON THE MAXIM THAT LEGITIMATE ACTIVITY WOULD BE PREFERRED TO ILLEGITIMATE ACTIVITY IF MORE MENTAL OR PHYSICAL EFFORT WERE REQUIRED OF THE LATTER. ONE MEASURE SUGGESTED WAS THE PARTICIPATION OF THE PUBLIC IN CRIME PREVENTION BY PAYING MORE ATTENTION TO SELF-PROTECTION. CHADWICK PROPOSED SEVERAL REFORM MEASURES DIRECTED AT MORE EFFICIENT LAW ENFORCEMENT. HIS PROPOSALS INCLUDED: (1) BASING POLICE WAGES ON PRODUCTIVITY; (2) CONSOLIDATING CRIME AND FIRE PREVENTIVE SERVICES INTO A SINGLE FORCE, IN ORDER TO PLACE MORE PREVENTIVE AGENTS IN THE FIELD; AND (3) INSTITUTING SUCH TECHNOLOGICAL INNOVATIONS AS IMPROVED STREET LIGHTING, VARIED ROUNDS FOR PATROLMEN, AND REPLACEMENT OF UNIFORMED OFFICERS WITH PLAINCLOTHESMEN. HE ALSO PROPOSED REFORMS TO STREAMLINE COURT PROCEDURE. MODERN ECONOMISTS AND SOCIAL SCIENTISTS ARE REVIEWING CHADWICK'S PROBLEMS AND SUGGESTIONS, AS MANY OF HIS PROGRAMS CAN BE APPLIED TO MODERN SOCIAL CONCERNS. REFERENCES ARE PROVIDED.