Leonard Porter Ayres (September 15, 1879 – October 29, 1946) was an American statistician. He played a central role in developing and analyzing large-scale statistical projects, especially for the Russell Sage Foundation. His best-known work dealt with comprehensive statistical studies of American casualties in the first and second world wars. Career Ayres was born at Niantic, Conn. His father was A clergymen and journalist, and editor of the Boston Advertiser. He received his college and graduate training at Boston University. Harvard University, and Columbia University, with a Ph.D. (1910) degree from Boston University. He began teaching in 1902 as one of the first to carry American ideas and methods to Puerto Rico. There he was appointed superintendent of schools in the districts of Caguas and San Juan, and in 1906 became general superintendent of all the public schools on the island. He founded the Insular Bureau of Statistics. Returning to live in the United States, Ayres was made head of the division of statistics in the Playground Association of America. Beginning in 1908, he was prominently identified with the work of the Russell Sage Foundation, especially as chairman of the committee in charge of the Backward Children Investigation. He co-authored a highly influential book on Laggards in Our Schools (1909) with Luther Halsey Gulick. They argued that the most important causes of retardation were environmental. He continued his studies of intelligence tests, and drafted widely adopted recommendations for yardsticks of student progress on intelligence tests for the elementary schools. Ayres found that curricula were typically fitted for the brightest rather than average student. He found that schools with low withdrawal rates were most efficient and economical. Historian Raymond Callahan has characterized as "mechanical" his methods of dealing with student retardation, elimination, and promotion. Furthermore he largely ignored social and educational factors, and he used non-comparable data. In 1908-09 Ayres lectured on education at New York University. On behalf of the American Statistical Association in 1915 Ayres became secretary of the Joint Committee on Standards for Graphic Presentation, which was chaired by Willard C. Brinton. In 1917 he was elected as a Fellow of the American Statistical Association. United States Army On behalf of the Russell Sage Foundation, in April 1917 Ayres organized the Division of Statistics of the Council of National Defense. In October he was assigned responsibility for statistical reporting and analysis for the War Industries Board, the Priorities