Improved Bounds on Restricted Isometry Constants for Gaussian Matrices

The Restricted Isometry Constants (RIC) of a matrix $A$ measures how close to an isometry is the action of $A$ on vectors with few nonzero entries, measured in the $\ell^2$ norm. Specifically, the upper and lower RIC of a matrix $A$ of size $n\times N$ is the maximum and the minimum deviation from unity (one) of the largest and smallest, respectively, square of singular values of all ${N\choose k}$ matrices formed by taking $k$ columns from $A$. Calculation of the RIC is intractable for most matrices due to its combinatorial nature; however, many random matrices typically have bounded RIC in some range of problem sizes $(k,n,N)$. We provide the best known bound on the RIC for Gaussian matrices, which is also the smallest known bound on the RIC for any large rectangular matrix. Improvements over prior bounds are achieved by exploiting similarity of singular values for matrices which share a substantial number of columns.Comment: 16 pages, 8 figure

Impact of the business environment on output and productivity in Africa

Africa is the poorest part of the world and it has the worst environment for long term business success by most standards. Empirical works normally find a negative correlation between income per worker and measures for poor business environment. This paper develops a general equilibrium model to assess the quantitative effects of the business environment, including access to finance, regulation, crime, corruption and infrastructure, on output and TFP for 30 Sub-Saharan African countries. We find that the quantitative effects of these areas of the business environment are large. They together can explain about 67% of the variation in income per capita relative to the US. Improving these dimensions of the business environment will be key for the long term development of the continent.Business environment, Investment Climate, African Development, Productivity

Impact of the business environment on output and productivity in Africa

We develop a general equilibrium model to assess the quantitative effects of the business environment, including regulation, crime, corruption, infrastructure and access to finance, on output and total factor productivity (TFP) for 30 Sub-Saharan African countries. The first four dimensions create inefficiencies at the firm level and are modeled as a tax on output. From the data, we find that on average firms in Africa lose a fifth of their sales due to those inefficiencies. On the other hand, poor access to credit affects the reallocation of resources across firms, capital formation and production scale. We find that the quantitative effects of these dimensions of the business environment are large, leading to decreases in output and TFP in the range of 40 to 77 percent and 18 to 44 percent respectively. Overall, they explain 67 percent of the variation in income per worker relative to the US.Business environment, Investment Climate, African Development, Productivity, Credit Constraints

A Critical Analytical and Historical Review of South African Published Life Tables

The paper gives a critical review of South African life tables published since the 1920s. The life tables were constructed on the assumption that vital registration was complete among whites, coloureds and Asians. Over time, robust measures of the life tables such as under-five mortality rate and life expectancy at birth have to show internal and external consistency. In addition, derived measures such as entropy, E, which summarises the degree of convexity of the life table survivorship function, l(x), and Anson’s U also have to display such consistency. Against these criteria, the paper sets out to assess the validity of South African life tables published since the 1920s

The Making, Unmaking and Remaking of a National but Stratified Vital Statistics System in the Republic of South Africa

The political history of South Africa had direct effect on the development of vital statistics in that country. The paper looks at the dynamics of the making, unmaking and remaking of a national but stratified vital statistics system in South Africa. The paper also outlines the crucial roles played by key players in the process. This historical context of vital statistics has implications for demographic teaching and research

Edgar M. to Mrs. S. Johansson (28 September 1962)

https://egrove.olemiss.edu/mercorr_pro/1978/thumbnail.jp

Indirect Estimation of Pre-Census Baseline In the Aftermath of a War

Pre-censal estimates help in proper planning for the execution of a census. After the end of a destabilizing war, these pre-censal estimates cannot be easily obtained. The paper proposes how pre-censal estimates can be obtained in the aftermath of a war using indirect estimation techniques. This involves the estimation of probabilities of mortality and of emigration obtained from survival models and multiple decrement life tables

Constraints to the Growth of Small Firms in Northern Myanmar

This paper uses survey data collected from Kalaymyo, a small urban city in North West Myanmar, to characterize firms and analyze the constraints limiting their growth. The level of firm ownership is very high but most firms are small, informal, operated out of the home, earning low income and with no employees. The most binding constraints are related to financing constraints, especially lack of access to informal credit. This is followed by the high degree of competition as the majority of firms are small retailers selling non-differentiated goods. This lack of credit combined with an apparent aversion to debt, limits the ability of entrepreneurs to take advantage of the high returns available on investment. We find that firms that made a capital investment over the last three years are significantly more profitable than those that did not

Human papilloma virus genotype distribution and risk factor analysis amongst reproductive aged women in urban Gambia

Purpose. Cervical cancer is the most frequently diagnosed female cancer in The Gambia, representing approximately 30% of cases. In 2014, the quadrivalent human papilloma virus (HPV) vaccine was introduced, which offers protection against HPV genotypes 6, 11, 16 and 18. To evaluate the potential effectiveness of this vaccine, genotype distribution and risk factor analysis were assessed. Methodology. Endocervical samples (n=232) were collected from women aged 20-49 years residing in urban Gambia. A questionnaire was administered to capture socio-demographic and cervical cancer risk factors. HPV detection and genotyping was performed by PCR amplification of the L1 major capsid gene and analysis of sequenced PCR products. Results/ Key Findings. The prevalence of HPV was 12% (28/232) and the high risk (HR) genotype HPV 52 (5/28) was the most prevalent genotype. HR-HPV sequences had high identity (≥ 90 %) to isolates which originated from America, Europe and Asia but not from Africa. Half (14/28) of participants were co-infected with Ureaplasma urealyticum/parvum, which increases the risk of progression to cervical cancer. Female genital mutilation and the use of hormone contraception for >5 years were identified as potential risk factors for HPV infection. Ethnicity-associated differences were also noted; participants of the Fula ethnic group had a higher prevalence of HR-HPV infection (31.3%) compared to the Mandinka (18.8%) and Wollof (12.5%) groups. Conclusion. These data may have a significant public health impact as the HPV quadrivalent vaccine may be of limited value if the circulating non-HPV 16/18 HR-genotypes are responsible for cytological abnormalities of the cervix