Geary, Robert Charles (‘Roy’) (1896–1983), statistician, was born in Dublin on 11 April 1896, the first child in the family of two sons and two daughters of Edmond Geary (who probably died in the late 1920s), an official in the general registrar's office, a keen mathematician and apparently a native of Careystown, Co. Cork, and his wife Jennie (née O'Sullivan), a native of Killarney, Co. Kerry. After an education at the model school, Glasnevin, and the O'Connell Schools, Geary studied at UCD (1913–18), where he obtained a B.Sc. (1916) and an M.Sc. (1917) in mathematics (both with first-class honours). Aided by a travelling scholarship he went on to study in Paris at the Sorbonne (1919–21). While in Paris he assisted the Sinn Féin diplomatic mission led by Seán T. O'Kelly (qv).
Geary entered the Irish civil service in 1923, and worked in the statistics branch of the Department of Industry and Commerce. When it was reorganised as the Central Statistics Office under the Department of the Taoiseach (1949), Geary was appointed director. On retiring from the civil service (31 March 1957) he became chief of the national accounts branch of the United Nations statistical office in New York (1957–60). He then returned to Ireland to become the first director of the newly formed Economic Research Institute (ERI; 1960–66). Geary was the author of over a hundred publications on mathematical and applied statistics and economics (listed by John Spencer in Conniffe (ed.), Roy Geary); he was awarded a D.Sc. by the NUI (1937), was elected MRIA (1938), and was a senior research fellow at the Cambridge University department of applied economics (1946–7). He received the Boyle medal for science from the RDS (1981), as well as honorary doctorates from the NUI (1962), QUB (1968), and TCD (1973); he was an honorary fellow of the Royal Statistical Society, the American Statistical Association, and the Institute of Mathematical Statistics, and president of the International Statistical Institute.
Geary's best-known work in statistics was concerned with the estimation of relationships where the random variables are subject to measurement error and with tests for normality and serial autocorrelation. His contiguity ratio for measuring spatial autocorrelation is still widely used by geographers. His contributions to economics include the eponymous Stone–Geary utility function and the ‘Geary’ method for evaluating real incomes at purchasing-power parities. Able, energetic, and creative, Geary was Ireland's most eminent statistician and had a passionate concern for social problems such as poverty and the costs of armaments. He believed that statistics narrowed differences between political parties and that an independent statistics office was a guarantee of civil liberties. In old age he remained active, regularly attending the annual Geary lecture of the Economic and Social Research Institute (as the ERI became), and contributing many letters to the Irish Times. He was from his youth a soccer enthusiast and from his time in Paris a music lover. Roy Geary (as he was best known) died in Dublin 8 February 1983. He married (1927) Mida Maura O'Brien (d. 1978) and with her had a son, Colm, and a daughter, Clodagh.