  Population growth (or decay) in a country can be due to various f
socio-economic constraints, as demonstrated in this paper. For example, sexual
intercourse is banned in various religions, during Nativity and Lent fasting
periods. Data consisting of registered daily birth records for very long
(35,429 points) time series and many (24,947,061) babies in Romania between
1905 and 2001 (97 years) is analyzed. The data was obtained from the 1992 and
2002 censuses, thus on persons alive at that time.
  We grouped the population into two categories (Eastern Orthodox and
Non-Orthodox) in order to distinguish religious constraints and performed
extensive data analysis in a comparative manner for both groups. From such a
long time series data analysis, it seems that the Lent fast has a more drastic
effect than the Nativity fast over baby conception within the Eastern Orthodox
population, thereby differently increasing the population ratio. Thereafter, we
developed and tested econometric models where the dependent variable is the
baby conception deduced day, while the independent variables are: (i) religious
affiliation; (ii) Nativity and Lent fast time intervals; (iii) rurality; (iv)
day length; (v) weekend, and (vi) a trend background. Our findings are
concordant with other papers, proving differences between religious groups on
conception, - although reaching different conclusions regarding the influence
of weather on fertility. The approach seems a useful hint for developing
econometric-like models in other sociophysics prone cases.
