EXPLORING ATTRITION BIAS: THE CASE OF THE KHAYELITSHA PANEL STUDY (2000-2004)

Attrition bias is a problem for users of panel data. Researchers need to know what socio‐economic factors are associated with attrition, and whether this is of relevance for the kind of analysis they want to conduct. This paper discusses attrition bias in the 2000/2004 Khayelitsha panel study. It shows that women, shack‐dwellers and people living in smaller households are more likely to attrit, but that the impact of these variables on the probability of attrition is relatively small. The implications for labour‐market analysis are then explored using Mincerian earnings functions and a probit regression on whether respondents are wage‐employed or not. The coefficients generated using a restricted sample of non‐attritors do not differ significantly from those generated by the entire sample. This suggests that attrition bias in this particular data set is not a problem for this kind of labour market analysis.     

Integration, social distress, and policy formation

I study the integration of regions in the form of a merger of populations, which I interpret as a revision of people’s social space and their comparison set; I illustrate the way in which a merger can aggravate social distress; and I consider policy responses. Specifically, I view the merger of populations as a merger of income vectors; I measure social distress by aggregate relative deprivation; I demonstrate that a merger increases aggregate relative deprivation; and I show that a social planner is able to reverse this increase by means of least-cost, post-merger increases in individual incomes, but is unable to counter it by relying exclusively on a self-contained income redistribution that retains individual levels of wellbeing at their pre-merger levels.     

The extension of social security coverage in developing countries

We study the dynamic general equilibrium effects of introducing a social pension program to elderly informal sector workers in developing countries who lack formal risk sharing mechanisms against income and longevity risks. To this end, we formulate a stochastic dynamic general equilibrium model that incorporates defining features of developing countries: a large informal sector, private transfers as an informal safety net, and a non-universal social security system. We find that the extension of retirement benefits to informal sector workers results in efficiency losses due to adverse effects on capital accumulation and the allocation of resources across formal and informal sectors. Despite these losses recipients of social pensions experience welfare gains as the positive insurance effects attributed to the extension of a social insurance system dominate. The welfare gains crucially depend on the skill distribution, private intra-family transfers and the specific tax used to finance the expansion.     

Learning or lock-in: Optimal technology policies to support mitigation

We investigate conditions that amplify market failures in energy innovations, and suggest optimal policy instruments to address them. Using an intertemporal general equilibrium model we show that ‘small’ market imperfections may trigger a several decades lasting dominance of an incumbent energy technology over a dynamically more efficient competitor, given that the technologies are very good substitutes. Such a ‘lock-in’ into an inferior technology causes significantly higher welfare losses than market failure alone, notably under ambitious mitigation targets. More than other innovative industries, energy markets are prone to these lock-ins because electricity from different technologies is an almost perfect substitute. To guide government intervention, we compare welfare-maximizing technology policies including subsidies, quotas, and taxes with regard to their efficiency, effectivity, and robustness. Technology quotas and feed-in-tariffs turn out to be only insignificantly less efficient than first-best subsidies and seem to be more robust against small perturbations.     

Income thresholds of dissaving in Germany: empirical evidence from the recent sample survey of income and expenditure (EVS 2008)

Saving of private households monotonically increases with income. If the regression lines, which represent the ‘demand for saving’, assume negative values, saving turns into dissaving, i.e. dissolving assets or going into debt. The zeros of the demand functions for saving are called ‘dissaving thresholds’. Dissaving thresholds for Germany are determined econometrically using the Sample Survey of Income and Expenditure. Dissaving thresholds turn out to be far higher than social assistance amounts. Implications for economic, social and consumer policy in Germany are discussed.     

The Displacement Effect of Public Pensions on the Accumulation of Financial Assets*

The generosity of public pensions may depress private savings and provide incentives to retire early. While there is plenty of evidence supporting the latter effect, there remains considerable controversy over whether public pensions crowd out private savings. This paper uses international micro‐data sets collected over recent years to investigate whether public pensions displace private savings. The identification strategy relies not only on cross‐country differences in generosity but also on differences in the progressivity or non‐linearity of pension formulas across countries. We estimate that an extra dollar of pension wealth depresses accumulated financial assets around the time of retirement by 22 cents. An extra 10,000 dollars in public pension wealth reduces the average retirement age by roughly one month, which implies an elasticity of years of retirement with respect to pension wealth of 0.15.     

Economic forecasting with evolved confidence indicators

We present a machine-learning method for sentiment indicators construction that allows an automated variable selection procedure. By means of genetic programming, we generate country-specific business and consumer confidence indicators for thirteen European economies. The algorithm finds non-linear combinations of qualitative survey expectations that yield estimates of the expected rate of economic growth. Firms’ production expectations and consumers’ expectations to spend on home improvements are the most frequently selected variables – both lagged and contemporaneous. To assess the performance of the proposed approach, we have designed an out-of-sample iterative predictive experiment. We found that forecasts generated with the evolved indicators outperform those obtained with time series models. These results show the potential of the methodology as a predictive tool. Furthermore, the proposed indicators are easy to implement and help to monitor the evolution of the economy, both from demand and supply sides.     

A worldwide analysis of trend in crop yields and yield variability: Evidence from FAO data

The trend in crop yields and yield variability affects food security and impact agricultural and food policies. Recent studies in this area have either focused only on one country or performed global analysis on a handful of crops. We provide the first worldwide analysis of trend and variability for 8088 country-crop yield series taken from the FAO database, employing a robust estimator to cope with the adverse statistical effects of outliers. More than half of the series display a slowdown in yield growth due to a closing of the gap between realised and attainable yields as well as to agricultural policies promoting more sustainable agricultural practices. Around one fourth of the series show also an increase in yield variability as a consequence of climate change and changes in farm management practices. Yield variability is highest in Eastern Europe, Central Asia and Middle East and North Africa, where food security may be threatened.     

Determinants of mobile broadband use in developing economies: Evidence from Sub-Saharan Africa

Broadband is seen as a vector of economic growth and social development. In the developing world, mobile technologies are widely adopted and mobile broadband is progressively rolled-out with high expectations on its impact on the countries’ development. We highlight what the determinants of mobile broadband use are in four Sub-Saharan countries. Using micro-level data coming from household surveys over 5 years, from 2013 to 2017, we show that SIM card ownership and being part of an online social community has a strong positive impact on mobile broadband use. We also highlight a positive correlation between digital inclusion and financial inclusion as mobile money users and bank account users are found to be more inclined to use mobile broadband. However, beyond apparent similarities, mobile broadband is used in different ways according to countries specificities. For instance, among the non-mobile owners in Nigeria, the unemployed are the most likely to use mobile broadband, most probably for job search practices, while it is rather used by students for information gathering in other countries. Finally we show that those excluded from mobile broadband use are the eldest, those with the lowest level of education, and women.     

Migrants' Home Town Associations and Local Development in Mali

We explore the impact of migrants' Home Town Associations (HTAs) on the provision of public goods in Mali. We combine an original dataset on all the HTAs created by Malian migrants in France from 1981 with census data on public goods in all Malian villages since 1976, and we run double‐difference estimations to compare villages with and without an HTA, before and after the creation of the HTAs. We find robust evidence that the provision of schools, health centers, and, to a lesser extent, water amenities has increased significantly faster in villages targeted by an HTA between 1987 and 2009 than in control villages.