Coombs, Lolagene C., and Ronald Freedman. "Premarital Pregnancy, Childspacing and Later Economic Achievement." Population Studies, 24, no. 3 (1970): 389-412.
The nature of the first-birth interval has a persistent, if diminishing relation to the family's economic position at successive observations in a longitudinal study of Detroit. The pre-maritally pregnant (PMP) were at a disadvantage at either the first (1961) observation or the fourth (1966) as compared with other married couples with either a short or long first birth interval (short-spacers and long-spacers). The PMP disadvantage was much greater for assets than for income, but disadvantage in each area persisted and was not a result of age, duration of marriage, or other factors likely to disappear in time. Poor education combined with early age at marriage was probably responsible. On the other hand, the economic disadvantages of the short-spacers (not PMP) as compared with the long-spacers, diminished consistently between 1961 and 1965. The initial disadvantage results from shorter marriage and career duration for husbands at each parity. At comparable marriage durations the difference disappears. Nevertheless, this means substantially smaller resources per head at the actual time of birth of successive children.