berman has also done field work among ultra-orthodox religious groups in israel. studying full-time yeshiva students, who berman finds study until 40 years old on average, and whose families have 7.6 children per woman (in the mid 1990s), he concludes that "subsidies induce dramatic reductions in labor supply and unparalleled increases in fertility." in a 2000 nber paper, berman describes ultra-orthodox jews as "a fascinating and fast-growing sect which has held virtual veto power over [israeli] public policy for more than two decades."