Quadratic spline fits by nonlinear least squares

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

Keywords

• fertility
• fertility models
• quadratic splines
• software