In 1970, seagoing pilots became retrospectively insurable, and gained full social security as members of the Non-Manual Workers Insurance Institute. That same year, a special regulation came into force for District Master Chimney Sweeps, making them fully insurable under the Craftsmans Insurance Scheme. An increase was made in tax-free allowances for children, which enabled 1,000,000 families to claim an allowance for the second child, compared to 300,000 families previously. The Second Modification and Supplementation Law (1970) increased the allowance for the third child from DM 50 to DM 60, raised the income-limit for the second child allowance from DM 7,800 to DM 13,200; subsequently increased to DM 15,000 by the third modification law (December 1971), DM 16,800 by the fourth modification law (November 1973), and to DM 18,360 by the fifth modification law (December 1973). A flexible retirement age after 62 years was introduced (1972) for invalids and handicapped persons, and social assistance was extended to those who previously had to be helped by their relatives. From 1971, special subventions were provided to enable young farmers to quit farming “and facilitate their entry into the non-agricultural pension system by means of back payments.”. How many more DM was in the fifth modification than the fourth?