Effects on Population Growth under Religious Conception Constraints in Romania Claudiu Herteliu 1 , Bogdan Vasile Ileanu 1 ,Marcel Ausloos 2,3,4 , Giulia Rotundo 5 1 The Bucharest University of Economic Studies, Bucharest, Romania 4 Royal Netherlands Academy of Arts and Sciences Joan Muyskenweg 25, 1096 CJ Amsterdam, The Netherlands 2 School of Management, University of Leicester, University Road, Leicester LE1 7RH, UK 3 GRAPES, r. Belle Jardini` ere, 483, B-4031 Liege, Wallonia-Brussels Federation 5 Sapienza University of Rome, Faculty of Economics, Department of Methods and models for Economics, Territory and Finance, via del Castro Laurenziano 9, I-00161 Roma, Italia May 17, 2022 Abstract Population growth (or decay) in a country can be due to various f socio-economic constraints, as demonstrated in this paper. For exam- ple, 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 1 arXiv:1509.04564v2 [physics.soc-ph] 24 Sep 2015