His studies were interrupted by the outbreak of World War II, and he eventually served in the Fourteenth Army in India.
He later married Katherine Juliet Grove-White, and the pair had a son, Donald James Roy, and two daughters.
He completed his Master of Arts in Economics at Cambridge in 1950, reading under Professor Edward Austin Gossage Robinson.
Roy (1951)[4] recognized that a major mechanism guiding assignment in the labor market is David Ricardo's principle of comparative advantage.
Selection among alternative occupations, as described by Roy, draws on notions of potential outcomes used in the literature on the design of experiments (Neyman, 1923;[8] Cox, 1958[9]).
Roy's selection phenomenon has been applied and extended to a wide range of other contexts, including: choice of market versus non-market work and wage comparisons (Gronau, 1974;[11] Heckman, 1974,[12] 1976;[13] Lewis, 1974[16]); and more general decision rules (see the survey in Heckman and Vytlacil, 2007a[17]).
His work also affected analysis of choice in: union versus non-union sectors (Lee, 1978[18]); levels of education (Willis and Rosen, 1979[19]); geographical region (Robinson and Tomes, 1982[20]); marital status (McElroy and Horney, 1981[21]); occupational choice (Miller, 1984[22]); piece rate versus salary pay structures (Lazear, 1986[23]); industry changers (Solon, 1988;[24] Gibbons and Katz, 1992[25]); immigration (Borjas, 1990[26]); and segmented labor markets (Magnac, 1991[27]).
His (1952)[5] paper is widely regarded as a contribution to portfolio theory co-equal with that of the Nobel-Prize winning analysis of Harry Markowitz (1952).