Volume 12 - Article 5 | Pages 105–106  

Quadratic spline fits by nonlinear least squares

By Carl Schmertmann

Abstract

This web program fits a Quadratic Spline model, as described in Schmertmann (2003; Demographic Research Volume 9, Article 5), to any empirical fertility schedule supplied by the user. The fit minimizes the sum of squared differences between the empirical nfx values and the nfx values from the QS model schedule. Output includes parameter estimates, a graphical depiction of the fitted schedule, and several text reports. Users do not need specialized statistical software or a particular operating system to run the program; the only requirement is a web browser.

Software
http://www.demographic-research.org/Volumes/Vol12/5/qsfit/qsfit.html

Author's Affiliation

• Carl Schmertmann - Florida State University, United States of America EMAIL

Other articles by the same author/authors in Demographic Research

Data errors in mortality estimation: Formal demographic analysis of under-registration, under-enumeration, and age misreporting
Volume 51 - Article 9

D-splines: Estimating rate schedules using high-dimensional splines with empirical demographic penalties
Volume 44 - Article 45

Revivorship and life lost to mortality
Volume 42 - Article 17

Editorial: The past, present, and future of Demographic Research
Volume 41 - Article 41

Stationary populations with below-replacement fertility
Volume 26 - Article 14

A system of model fertility schedules with graphically intuitive parameters
Volume 9 - Article 5

Estimating Parametric Fertility Models with Open Birth Interval Data
Volume 1 - Article 5

Most recent similar articles in Demographic Research

The short- and long-term determinants of fertility in Uruguay
Volume 51 - Article 10    | Keywords: fertility, panel data, stages of female reproductive life, time series, Uruguay

The big decline: Lowest-low fertility in Uruguay (2016–2021)
Volume 50 - Article 16    | Keywords: adolescent fertility, birth order, fertility, Latin America, ultra-low fertility, Uruguay

Cohort fertility of immigrants to Israel from the former Soviet Union
Volume 50 - Article 13    | Keywords: age at first birth, assimilation, cohort analysis, fertility, immigration, parity, religiosity

Fertility decline, changes in age structure, and the potential for demographic dividends: A global analysis
Volume 50 - Article 9    | Keywords: age structure, demographic dividend, demographic transition, fertility, migration, population momentum, working-age population

Analyzing hyperstable population models
Volume 49 - Article 37    | Keywords: birth trajectory, cohort analysis, cyclical populations, dynamic population model, fertility, hyperstable, period