The length of the existence of parental leave rights in a country has an additional effect on its prevalence. In general, for each indicator to be comparable across time and countries, it is crucial that countries use similar concepts and methods in their calculation. Available at: http://www.ilo.org/dyn/normlex/en/f?p=NORMLEXPUB:12100:0::NO :12100:P12100_INSTRUMENT_ID:312301:NO ILO, 1981: The Workers with Family Responsibilities Recommendation, 1981 (No. Available at: http://www.ilo.org/dyn/normlex/en/f?p=NORMLEXPUB:12100:0::NO :12100:P12100_INSTRUMENT_ID:312503:NO ILO, 2000: Maternity Protection Recommendation, 2000 (No.