University of Southampton Research Repository ePrints Soton Copyright © and Moral Rights for this thesis are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder/s. The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders. When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given e.g. AUTHOR (year of submission) "Full thesis title", University of Southampton, name of the University School or Department, PhD Thesis, pagination http://eprints.soton.ac.uk UNIVERSITY OF SOUTHAMPTON An Analysis of Fertility Differentials in Liberia and Ghana Using Multilevel Models. By Nicholas John Parr Doctor of Philosophy Department of Social Statistics, Faculty of Social Sciences April 1992 UNIVERSITY OF SOUTHAMPTON ABSTRACT FACULTY OF SOCIAL SCIENCES DEPARTMENT OF SOCIAL STATISTICS Doctor of Philosophy AN ANALYSIS OF FERTILITY DIFFERENTIALS IN LIBERIA AND GHANA USING MULTILEVEL MODELS by Nicholas John Parr This thesis investigates differentials in the levels of fertility, nuptiality and contraceptive use in Liberia and Ghana, using data from the recent Demographic and Health Surveys in these countries. Of particular interest is the effect of the community in which a woman lives on her current and past fertility, her marital status and her use of contraception. This interest stems from the fact that, although the community in which a woman lives is integral to anthropological explanations of fertility, statistical models of fertility have rarely included an assessment of community effects. The method of analysis used is multilevel modelling. This involves fitting variables measured at the woman level, variables measured at the community level and also includes the use of random effects to assess the extent to which community effects have not been captured by the fixed explanatory variables. Multilevel log-linear models are used in the analyses of fertility and multilevel logistic models are used in the analyses of nuptiality and contraceptive use. This thesis demonstrates not only that there is significant variation between communities in both Liberia and Ghana for number of births 0-4 years before survey, children ever born, marital status and use of contraception but also that in each case significant community effects are found even after controlling for woman's age, education, religion and ethnicity. Acknowledgements I am most grateful to Dr. Ian Diamond, Dr. Andrew Hinde and Mr. Philip Cooper all of the Department of Social Statistics, Southampton University for their supervision of this work. I would like to thank Professor Grayham Mizon of the Department of Economics, the European University Institute and Dr. Maozu Lu of the Department of Economics, Southampton University for their comments on Chapter 3 of this thesis. I would also like to thank Dr. Jim Milne of the Department of Geography, Southampton University for digitising the outlines of the maps of Liberia and Ghana. I would like to thank the Liberian Ministry of Planning and Economic Affairs for their hospitality during my fieldwork in Liberia and express my hope for the well-being of all those people who were hospitable to me during my time in Liberia. I hereby acknowledge the Ghana Statistical Service for their permission to use the Ghana Demographic and Health Survey data. This work was undertaken with the assistance of award no. R00428824168 frmn ESRC. Contents Page Abstract Acknowledgements List of Tables. List of Maps, Figures and Photos. Chapter 0: Introduction. 1 0.1 Background 1 0.2 Alms of This Thesis 1 0.3 Summary of Existing Knowledge 3 0.4 Outline of Thesis 4 Chapter 1: Fertility in Sub-Saharan Africa. 6 1.0 Introduction 6 1.1 A Framework for the Analysis of Fertility 6 1.1.1 The Determinants of Fertility 6 1.1.2 Bongaarts' Model 10 1.2 Fertility Levels in Sub-Saharan Africa 15 1.2.0 Introduction 15 1.2.1 Fertility Differentials 18 1.3 The Determinants of Fertility in Sub-Saharan Africa 22 1.3.0 Introduction 22 1.3.1 Marriage 23 1.3.2 Contraception 32 1.3.3 Abortion 40 1.3.4 Postpartum Non-Susceptibility 41 1.3.5 Sterility 48 1.3.6 Other Factors 50 1.4 Summary 51 Chapter 2; Multilevel Models. 52 2.0 Introduction 52 2.1 Hierarchical Structures and Survey Analysis 52 2.2 Some Methods of Statistical Analysis Which Do Not 55 Consider the Hierarchical Structure of Data Properly 2.2.0 Introduction 55 2.2.1 Regression/Analysis of Covariance 55 2.2.2 Generalized Linear Models 62 2.2.3 Slopes-as-Outcomes 64 2.3 The Multilevel Model 67 2.3.0 Introduction 67 2.3.1 The Linear Multilevel Model 68 2.3.1.1 The Linear Two-level Model 71 2.3.1.2 Linear Models with Two or More Levels 93 2.3.2 The General ( Nonlinear ) Multilevel Model 96 Chapter 3: The Methodology of Encompassing and its 99 Implications for Demographic Research 3.0 Introduction 99 3.1 Models and Model Evaluation 100 3.2 The Encompassing Principle 102 3.3 Implications of the Encompassing Methodology 107 3.3.1 Emphasis of Model Comparison 107 Over Model Selection 3.3.2 Preference for a General to Simple Approach 108 Over Simple to General 3.4 Evaluating the Encompassing Methodology 109 3.5 Examples of the Application of Encompassing 112 3.5.1 Comparisons of OLS Regression Models 113 3.5.2 Comparison of Multilevel Models 115 3.6 Model Selection for Multilevel Models: A Postscript 119 3.7 Application of Encompassing in this Research 121 Chapter 4: A Case for a Multilevel Approach to 123 Analysing Fertility. 4.0 Introduction 4.1 Macro-level Influences on Individual-level Fertility 124 4.2 Relating Macro-level Analyses of Fertility Back to 133 the Individual Level 4.3 Conclusions/Implications for Statistical Analyses 136 Chapter 5: Liberia. 13 9 5.1 Introduction 139 5.2 A Review of Research on Fertility in Liberia " 14 6 5.2.1 Introduction 146 5.2.2 Fertility Differentials 147 5.2.3 The Proximate Determinants of Fertility 151 5.2.3.1 Marriage 151 5.2.3.2 Contraception 153 5.2.3.3 Abortion 163 5.2.3.4 Postpartum Non-Susceptibility 164 5.2.3.5 Sterility 166 5.2.4 Fertility and the Proximate Determinants 167 5.3 The Liberia Demographic and Health Survey 168 5.3.1 Characteristics of the Women Surveyed 168 5.3.2 The Proximate Determinants of Fertility 176 5.3.2.1 Marriage 17 6 5.3.2.2 Contraception 181 5.3.2.3 Postpartum Non-Susceptibility 186 5.3.2.4 Sterility 191 5.3.3 Fertility Differentials 192 5.3.3.1 Fertility and the 192 Proximate Determinants 5.3.3.2 Fertility Differentials by Background 196 Characteristics 5.4 Differentials in Fertility Between Communities 203 5.4.0 Introduction 203 5.4.1 Method of Summary of Between-Community 204 Differentials in Fertility 5.4.2 Differentials in the Proximate Determinants 206 of Fertility Between Communities 5.4.2.1 Marriage 206 5.4.2.2 Contraception 209 5.4.3 Differentials in Fertility Between Communities 215 5.5 Multilevel Models of Fertility in Liberia 220 5.5.0 Introduction 220 5.5.1 Preliminary Considerations 222 5.5.1.1 The Response Variables Chosen 222 5.5.1.2 The Explanatory Variables Chosen 223 5.5.1.3 The Choice of Representation 227 of Communities 5.5.1.4 The Choice of Link Functions 231 5.5.1.5 Interpretation of the Parameters of 232 Nonlinear Multilevel Models 5.5.1.6 The Use of Differential Weights 235 5.5.1.7 The Choice of Software 235 5.5.2 Results 236 5.5.2.1 The Proximate Determinants of Fertility 236 5.5.2.1.1 Marriage 23 6 5.5.2.1.2 Contraception 242 5.5.2.2 Fertility 255 5.6 Discussion 272 Appendix 5A 274 Appendix 5B 275 Appendix 5C 27 8 Appendix 5D 281 Appendix 5E 284 Appendix 5F 287 Appendix 5G 2 91 Appendix 5H 2 93 Chapter 6: Ghana. 2 95 6.1 Introduction 295 6.2 A Review of Research on Fertility in Ghana 296 6.2.1 Introduction 296 6.2.2 The Proximate Determinants of Fertility 299 6.2.2.1 Marriage 299 6.2.2.2 Contraception 303 6.2.2.3 Abortion 305 6.2.2.4 Postpartum Non-Susceptibility 306 6.2.2.5 Sterility 308 6.2.2.6 Other Factors 308 6.2.3 Fertility Differentials 308 6.3 The Ghana Demographic and Health Survey 312 6.3.1 Characteristics of the Women Surveyed 313 6.3.2 The Proximate Determinants of Fertility 318 6.3.2.1 Marriage 318 6.3.2.2 Contraception 324 6.3.2.3 Postpartum Non-Susceptibility 330 6.3.2.4 Sterility 336 6.3.3 Fertility Differentials 336 6.3.3.0 Introduction 336 6.3.3.1 Fertility and the Proximate Determinants337 6.3.3.2 Fertility Differentials by Background 341 Characteristics 6.4 Differentials in Fertility Between Communities 34 9 6.4.0 Introduction 349 6.4.1 Differentials in the Proximate Determinants 350 of Fertility Between Communities 6.4.1.1 Marriage 350 6.4.1.2 Contraception 353 6.4.2 Differentials in Fertility Between Communities 359 6.5 Multilevel Models of Fertility in Ghana 365 6.5.0 Introduction 365 6.5.1 Preliminary Considerations 366 6.5.1.1 The Choice of Response Variables 366 6.5.1.2 The Explanatory Variables Chosen 367 6.5.1.3 The Choice of Representation 3 68 of Communities 6.5.1.4 The Choice of Link Functions 369 5.5.1.5 The Choice of Software 370 6.5.2 Results 370 6.5.2.1 The Proximate Determinants of Fertility 370 6.5.2.1.1 Marriage 370 6.5.2.1.2 Contraception 37 6 6.5.2.2 Fertility 388 6.6 Discussion 404 Appendix 6A 4 07 Appendix 6B 410 Appendix 6C 413 Appendix 6D 416 Appendix 6E 419 Appendix 6F 422 Appendix 6G 423 Appendix 6H 425 Appendix 61 427 Chapter 7: A Comparison of Fertility in Liberia and Ghana.