The world's Jewish population is estimated at 13,854,800 at the beginning of 2013 by Sergio DellaPergola.
This was an increase of 101,500 (0.74%) over the 2012 estimate by the author (revised from the 2012 version published at the Berman Jewish DataBank). Since the world's total population increased by 1.16% in 2012, DellaPergola notes that world Jewry hence increased at less than two thirds of the general world population growth rate.
Please note that several definitions of persons counting as Jewish are discussed by the author, including expanded definitions and core definitions. Figure 3 (page 16 of the PDF) has an interesting and useful schematic summary of the definitional possibilities.
The core estimate for the United States is approximately 5,425,000, second to the Israel estimate of 6,014,300.
This article, World Jewish Population 2013, is reprinted as Current Jewish Population Reports, # 9, 2013 of the Berman Jewish DataBank at the Jewish Federations of North America, and is posted with permission of Springer, the new publisher of the American Jewish Year Book. It was originally published as Sergio DellaPergola. “World Jewish Population, 2013,” in the The American Jewish Year Book, 2013, Volume 113 (2013).