Academic Journals Database
Disseminating quality controlled scientific knowledge

Spline interpolation of demographic data revisited

Author(s): Nittaya McNeil | Patarapan Odton | Attachai Ueranantasun

Journal: Songklanakarin Journal of Science and Technology
ISSN 0125-3395

Volume: 33;
Issue: 1;
Start page: 117;
Date: 2011;
VIEW PDF   PDF DOWNLOAD PDF   Download PDF Original page

Keywords: natural cubic spline | monotonic | fertility | population | mortality

Spline functions have been suggested in demographic research for interpolating age-specific data as they have desirablesmoothness optimality properties. However, difficulties arise when boundary conditions need to be satisfied. Anadditional problem is that age-specific demographic data functions are necessarily non-negative, requiring the interpolatingspline to be monotonic non-decreasing. In this paper we describe a simple and effective alternative that circumvents theseproblems. We show that natural cubic splines can be used to interpolate age-specific demographic data and ensure thatrelevant boundary conditions on second derivatives are satisfied, thus preserving the desirable optimality property of theinterpolating function without the need to increase the degree of the spline function. The method involves incorporating oneor two additional strategically placed knots with values estimated from the data. We describe how the method works forselected fertility, population, and mortality data.
Save time & money - Smart Internet Solutions     

Tango Rapperswil
Tango Rapperswil