Internal Migration, Selection Bias and Human Development: Evidence from Indonesia and Mexico

The aim of this paper is to measure the returns to migration using non-experimental data taking both observed and unobserved characteristics into account. A significant challenge related to migration research and the issues of unobserved heterogeneity is that the standard 2stage least squares estimator (2SLS) is strictly only applicable to situations with linear and continuous treatment and outcomes, both of which are not appropriate for models of migration and many outcomes of interest. Furthermore, migration is not always a binary process given that people migrate to city or non-city locations and some migrants do return. Introducing these multinomial treatment effects means that one cannot rely on standard 2SLS methods. Using panel data from Indonesia (Indonesia Family Life Survey—IFLS) and Mexico (Mexican Family Life Survey— MxFLS) and applying non-linear instrumental variable (Heckman’s treatment effects model) and maximum simulated likelihood models, we measure the impacts of migration on a broad range of variables that include socio economic outcomes such as consumption, nutrition, health status and emotional well-being for adult household members and health and schooling outcomes for children. We find consistent results for both countries that point to significant trade-offs related to migration. We found that migration can greatly improve socio-economic status through increases in income or consumption but can also be detrimental to the health status and emotional well-being of migrants and/or their extended families.The aim of this paper is to measure the returns to migration using non-experimental data taking both observed and unobserved characteristics into account. A significant challenge related to migration research and the issues of unobserved heterogeneity is that the standard 2stage least squares estimator (2SLS) is strictly only applicable to situations with linear and continuous treatment and outcomes, both of which are not appropriate for models of migration and many outcomes of interest. Furthermore, migration is not always a binary process given that people migrate to city or non-city locations and some migrants do return. Introducing these multinomial treatment effects means that one cannot rely on standard 2SLS methods. Using panel data from Indonesia (Indonesia Family Life Survey—IFLS) and Mexico (Mexican Family Life Survey— MxFLS) and applying non-linear instrumental variable (Heckman’s treatment effects model) and maximum simulated likelihood models, we measure the impacts of migration on a broad range of variables that include socio economic outcomes such as consumption, nutrition, health status and emotional well-being for adult household members and health and schooling outcomes for children. We find consistent results for both countries that point to significant trade-offs related to migration. We found that migration can greatly improve socio-economic status through increases in income or consumption but can also be detrimental to the health status and emotional well-being of migrants and/or their extended families.

Internal Migration, Selection Bias and Human Development: Evidence from Indonesia and Mexico

The aim of this paper is to measure the returns to migration using non-experimental data taking both observed and unobserved characteristics into account. A significant challenge related to migration research and the issues of unobserved heterogeneity is that the standard 2stage least squares estimator (2SLS) is strictly only applicable to situations with linear and continuous treatment and outcomes, both of which are not appropriate for models of migration and many outcomes of interest. Furthermore, migration is not always a binary process given that people migrate to city or non-city locations and some migrants do return. Introducing these multinomial treatment effects means that one cannot rely on standard 2SLS methods. Using panel data from Indonesia (Indonesia Family Life Survey—IFLS) and Mexico (Mexican Family Life Survey— MxFLS) and applying non-linear instrumental variable (Heckman’s treatment effects model) and maximum simulated likelihood models, we measure the impacts of migration on a broad range of variables that include socio economic outcomes such as consumption, nutrition, health status and emotional well-being for adult household members and health and schooling outcomes for children. We find consistent results for both countries that point to significant trade-offs related to migration. We found that migration can greatly improve socio-economic status through increases in income or consumption but can also be detrimental to the health status and emotional well-being of migrants and/or their extended families.Migration, selection, non-linear instrumental variables, consumption, socio-economic mobility, health, education

Finite Mixture Models

Finite mixture models provide a natural way of modeling continuous or discrete outcomes that are observed from populations consisting of a finite number of homogeneous subpopulations. Applications of finite mixture models are abundant in the social and behavioral sciences, biological and environmental sciences, engineering and finance. Such models have a natural representation of heterogeneity in a finite, usually small, number of latent classes, each of which may be regarded as a type. More generally, the finite mixture model can be shown to approximate any unknown distribution under suitable regularity conditions. The Stata package -fmm- implements a maximum likelihood estimator for a class of finite mixture models. In this talk, I will begin by introducing finite mixture models using a number of examples and discuss issues of estimation, testing and model selection. I will then describe estimation using fmm, calculations of predictions, marginal effects, and posterior class probabilities, and illustrate these using examples from econometrics and finance.

Strength and permeation properties of slag blended fly ash based geopolymer concrete

Geopolymer is a binder that can act as an alternative of Portland cement. Geopolymers use by-product substances such as fly ash, and can help reduce carbon dioxide emission of concrete production. This paper presents the results of a study on the fly ash based geopolymer concrete suitable for curing at ambient temperature. To activate the fly ash, a combination of sodium hydroxide and sodium silicate solutions was used. The setting and hardening of geopolymer concrete were obtained by blending blast furnace slag with fly ash instead of using heat curing. Ground granulated blast furnace slag (GGBFS) was used at the rate of 10% or 20 % of the total binder. The tests conducted include compressive strength, tensile strength, flexure strength, sorptivity and volume of permeable voids (VPV) test. The geopolymer concrete compressive strength at 28 days varied from 27 to 47 MPa. Results indicated that the strength increased and water absorption decreased with the increase of the slag content in the geopolymer concrete. In general, blending of slag with fly ash in geopolymer concrete improved strength and permeation properties when cured in ambient temperature

Properties of fly ash and slag blended geopolymer concrete cured at ambient temperature

The properties of concrete using fly ash based geopolymer as the binder were shown in recent studies. However, most of the previous studies focused on the properties of geopolymer concrete samples cured at high temperature. In this study, fly ash based geopolymer concrete suitable for curing at ambient temperature was designed and some durability properties were investigated. Geopolymer mixtures were prepared with fly ash as the primary binder which was activated by a mixture of sodium silicate and sodium hydroxide solutions. Ground granulated blast furnace slag (GGBFS) was added as 0%, 10% and 20 % of the total binder. Samples were also cast from an ordinary Portland cement (OPC) concrete mixture in order to compare with the properties of geopolymer and OPC concretes. All the concrete samples were ambient-cured (15-20°C) after casting until tested. The tests conducted include compressive strength, drying shrinkage, sorptivity and volume of permeable voids (VPV) test. The strength of the geopolymer concretes enhanced from the early age and continued to develop in similar trend as OPC concrete. Strength increased with the increase of slag in the mixture. The geopolymer concretes showed drying shrinkage, sorptivity and VPV values comparable to those of the control OPC concrete. In general, the results show that it is possible to design fly ash and slag blended geopolymer concrete suitable for ambient curing with similar or better durability properties of conventional OPC concrete

The effects of ground granulated blast-furnace slag blending with fly ash and activator content on the workability and strength properties of geopolymer concrete cured at ambient temperature

Inclusion of ground granulated blast-furnace slag (GGBFS) with class F fly-ash can have a significant effect on the setting and strength development of geopolymer binders when cured in ambient temperature. This paper evaluates the effect of different proportions of GGBFS and activator content on the workability and strength properties of fly ash based geopolymer concrete. In this study, GGBFS was added as 0%, 10% and 20% of the total binder with variable activator content (40% and 35%) and sodium silicate to sodium hydroxide ratio (1.5–2.5). Significant increase in strength and some decrease in the workability were observed in geopolymer concretes with higher GGBFS and lower sodium silicate to sodium hydroxide ratio in the mixtures. Similar to OPC concrete, development of tensile strength correlated well with the compressive strength of ambient-cured geopolymer concrete. The predictions of tensile strength from compressive strength of ambient-cured geopolymer concrete using the ACI 318 and AS 3600 codes tend to be similar to that for OPC concrete. The predictions are more conservative for heat-cured geopolymer concrete than for ambient-cured geopolymer concrete

Durability of fly ash based geopolymer concrete

Inclusion of ground granulated blast furnace slag (GGBFS) together with fly-ash can have significant effects on the development of mechanical and durability properties of geopolymer concrete when cured at normal temperature. The slag blended geopolymer concretes showed durability properties comparable to those of the control OPC concrete. In general, the results show that it is possible to design fly ash and slag blended geopolymer concrete suitable for ambient curing with similar or better durability properties of conventional OPC concrete