Does Human Capital Protect Workers against Exogenous Shocks? South Africa in the 2008-2009 Crisis

The financial and economic crisis of 2008 and 2009 has taken its toll on the South African economy. The economy contracted for the first time since 1998, and entered recession during the fourth quarter of 2008. The GDP contraction was soon transmitted to the labor market. Between the second quarters of 2008 and 2009, employment fell by 3.8 percent. However, not all individuals were hit with the same intensity. Using labor force survey data unique in the African context, we find that human capital provided a buffer against the shock. After controlling for observable characteristics, education and experience showed the potential to entirely offset the effect of the recession on the likelihood of employment. This has important policy implications, as it strengthens the case for strategic investments in human capital, and helps identifying the unskilled as those with the highest need for social safety net interventions during the recession.labor markets, South Africa, financial crisis, human capital, business cycle, emerging economies

Working Paper 106 - Does Human Capital Protect Workers against Exogenous Shocks? South Africa in the 2008 - 2009 Crisis

The financial and economic crisis of 2008and 2009 has taken its toll on the SouthAfrican economy. The economy contractedfor the first time since 1998, and enteredrecession during the fourth quarter of 2008.The GDP contraction was soon transmittedto the labor market. Between the secondquarters of 2008 and 2009, employment fellby 3.8 percent. However, not all individualswere hit with the same intensity. Using laborforce survey data unique in the Africancontext, we find that human capital provideda buffer against the shock. After controllingfor observable characteristics, education andexperience showed the potential to entirelyoffset the effect of the recession on thelikelihood of employment. This has importantpolicy implications, as it strengthens thecase for strategic investments in humancapital, and helps identifying the unskilled asthose with the highest need for social safetynet interventions during the recession.

Investigating Metastatic Lineage in Colorectal Cancer by Single Cell DNA Sequencing

Metastasis is the primary cause of human cancer deaths. Patients with metastatic colorectal cancer (mCRC) show only an 11% 5-year survival rate, compared to those without local or distant metastases (92% 5-year survival rate). Understanding the CRC tumor evolution may provide valuable insights on how to improve treatment in patients with mCRC. However, the genomic basis of metastasis has been difficult to study, in part due to the extensive intratumor heterogeneity at both the primary and metastatic tumor sites, and the low frequency of subclones with metastatic potential. Previous studies have applied conventional bulk next-generation sequencing (NGS) methods, which have limited ability to resolve intratumor heterogeneity. To address this problem, we have developed a highly-multiplexed single cell DNA sequencing method that combines flow-sorting of single nuclei, multiple-displacement-amplification using Φ29 polymerase, low-input library preparation, library barcoding, targeted capture and NGS to generate high-coverage data from single cells. We validate this method by generating high coverage sequencing data from single human cells, with low allelic dropout and high detection efficiencies for single nucleotide variants. Using this method, we sequenced 186 single cells from primary tumor and liver metastases from two mCRC patients to delineate the clonal architecture of the tumor and reconstruct their phylogenetic lineages. We also performed exome sequencing on the bulk tumor tissues. Our data identified a large number of nonsynonymous mutations that evolved in the root node during the earliest stage of primary tumor evolution and were maintained in all single cells during the clonal expansion of the tumor mass. We also identified a small number of mutations that were specific to the liver metastases, which are likely to play an important role in metastatic dissemination. Furthermore, we found three diploid cells with only APC mutations in CO5, which may represent the progenitor clones that gave rise to the primary and metastatic tumors. Using the single cell data, we construct phylogenetic trees, which revealed branched evolution in metastasis. Our data suggest that both mCRC patients are consistent with the late-dissemination model, in which the primary tumors evolved for a long period of time prior to the dissemination of clones to distant organ sites. In summary, we have developed novel methods for single cell DNA sequencing, and applied these methods to gain unprecedented understanding of clonal evolution during metastasis in colorectal cancer

How Large Is the Private Sector in Africa? Evidence from National Accounts and Labor Markets

In recent years, the private sector has been recognized as a key engine of Africa's economic development. Yet, the most simple and fundamental question remains unanswered: how large is the African private sector? We present novel estimates of the size of the private sector in 50 African countries derived from the analysis of national accounts and labor market data. Our results point to a relatively large size of the African private sector. National account data shows that this accounts for about 2/3 of total investments, 4/5 of total consumption and 3/4 of total credit. In relative terms, large private sector countries are concentrated in Western Africa (Cote d'Ivoire, Guinea, Niger, Senegal and Togo), Central Africa (Cameroun, Republic of Congo) and Eastern Africa (Kenya, Sudan, Uganda and Tanzania), with the addition of Mauritius. Countries with small private sectors include a sample of oil-exporters (Algeria, Angola, Equatorial Guinea, Libya and Nigeria), some of the poorest countries in the continent (Burundi, Burkina Faso, Guinea Bissau, Mali and Sao Tome e Principe), Zambia and Botswana. Over the last ten years, the size of the private sector has been contracting significantly in oil exporting countries, although the variation in its size does not appear to be significantly correlated with growth performance. Labor market data reinforces the idea of a large private sector, which provides about 90% of total employment opportunities. However, most of this labor is informal and characterized by low productivity: permanent wage jobs in the private sector account on average for only 10% of total employment (a share similar to that provided by public administration and state owned enterprises). South Africa is the notable exception, with formal wage employment in the private sector representing 46% of total employment. Finally, we find evidence of negative private sector earning premiums, suggesting that market distortions abound. These are likely to prevent the efficient allocation of human resources, and to reduce the overall productivity of the African economies.private sector size, private sector development, private consumption, private investment, national accounts, private sector employment, private sector earnings, labor markets, Africa

Lifetime and polarization of the radiative decay of excitons, biexcitons and trions in CdSe nanocrystal quantum dots

Using the pseudopotential configuration-interaction method, we calculate the intrinsic lifetime and polarization of the radiative decay of single excitons (X), positive and negative trions (X+ and X−), and biexcitons (XX) in CdSe nanocrystal quantum dots. We investigate the effects of the inclusion of increasingly more complex many-body treatments, starting from the single-particle approach and culminating with the configuration-interaction scheme. Our configuration-interaction results for the size dependence of the single-exciton radiative lifetime at room temperature are in excellent agreement with recent experimental data. We also find the following. (i) Whereas the polarization of the bright exciton emission is always perpendicular to the hexagonal c axis, the polarization of the dark exciton switches from perpendicular to parallel to the hexagonal c axis in large dots, in agreement with experiment. (ii) The ratio of the radiative lifetimes of mono- and biexcitons (X):(XX) is ~1:1 in large dots (R=19.2 Å). This ratio increases with decreasing nanocrystal size, approaching 2 in small dots (R=10.3 Å). (iii) The calculated ratio (X+):(X−) between positive and negative trion lifetimes is close to 2 for all dot sizes considered

Does human capital protect workers against exogenous shocks? South Africa in the 2008 - 2009 crisis

The financial and economic crisis of 2008 and 2009 has taken its toll on the South African economy. The economy contracted for the first time since 1998, and entered recession during the fourth quarter of 2008. The GDP contraction was soon transmitted to the labor market. Between the second quarters of 2008 and 2009, employment fell by 3.8 percent. However, not all individuals were hit with the same intensity. Using labor force survey data unique in the African context, we find that human capital provided a buffer against the shock. After controlling for observable characteristics, education and experience showed the potential to entirely offset the effect of the recession on the likelihood of employment. This has important policy implications, as it strengthens the case for strategic investments in human capital, and helps identifying the unskilled as those with the highest need for social safety net interventions during the recession