Overview
José Antonio Ortega is a demographer at the Universidad Autónoma de Madrid (Department of Economic Analysis). His research focuses on low fertility measurement, tempo effects, parity-specific analysis, and demographic methods. He is best known for co-developing (with Hans-Peter Kohler) the Kohler-Ortega (K-O) framework for tempo adjustment of parity-specific fertility rates using occurrence-exposure intensities rather than incidence rates, which avoids the compositional bias in the Bongaarts-Feeney (1998) procedure.
Key Contributions / Features
- Ortega and Kohler (2002, MPIDR WP): Methodological synthesis introducing the K-O framework for parity-specific tempo adjustment using fertility intensities; defines the Period Fertility Index (PF) as the quantum measure free from tempo and compositional effects; proposes TFR=(1−r)(1+d)⋅PF decomposition.
- Kohler and Ortega (2004, book chapter): Extended overview of the K-O framework with Italy/Czech Republic empirical calibration (BF over-adjustment of 7–17%), the four-factor birth-count decomposition (adding mean generation size G), cohort completion under "postponement stops" vs. "postponement continues" scenarios, and the fertility ageing effect concept.
- Kohler, Billari, and Ortega (2002, PDR): Co-author of the paper establishing the concept and empirical measurement of "lowest-low fertility" (TFR < 1.3) in Southern and Eastern Europe, attributing it to tempo effects amplified by social interaction mechanisms.
- Kohler, Billari, and Ortega (2006, book chapter): Extended policy synthesis developing the four-factor causal framework (rational postponement, social interactions, tempo distortions, work-family incompatibility); documented cross-OECD correlation reversals from 1975 to 1996 (TFR×FLFP, TFR×marriage rate, TFR×divorce rate, TFR×extra-marital births); quantified negative population momentum (−35% women 20–35 in Europe by 2040); defined Postponement Transition onset criterion.
- Kohler and Ortega (2001): Primary K-O papers developing the intensity-based tempo adjustment framework applied to Austria and Sweden.
- Ortega and Poncela (2005, IJF): Co-developer of a Non-Stationary Dynamic Factor Model (DFM) for jointly forecasting TFR trends in Southern European countries; shows forecast gains over univariate ARIMA at horizons of 3+ years (~1/3 RMSE reduction at 10 years); documents failure of ARIMA-with-trend at long horizons.
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