> table(india_40$year_of_birth, india_40$version_number) 23 42 52 74 1942 36 0 0 0 1943 376 0 0 0 1944 515 0 0 0 1945 493 0 0 0 1946 494 0 0 0 1947 742 0 0 0 1948 598 0 0 0 1949 564 271 0 0 1950 684 565 0 0 1951 628 555 0 0 1952 773 564 0 0 1953 205 745 0 0 1954 0 702 0 0 1955 0 643 0 0 1956 0 794 423 0 1957 0 712 835 0 1958 0 893 811 0 1959 0 262 817 0 1960 0 5 1258 0 1961 0 0 1009 0 1962 0 0 1041 0 1963 0 0 1185 0 1964 0 0 1183 0 1965 0 0 1539 824 1966 0 0 529 2807 1967 0 0 0 3958 1968 0 0 0 3682 1969 0 0 0 4231 1970 0 0 0 5710 1971 0 0 0 4037 1972 0 0 0 4215 1973 0 0 0 4316 1974 0 0 0 4670 1975 0 0 0 4876 1976 0 0 0 1541