Outlook for alternative energy sources

Predictions are made concerning the development of alternative energy sources in the light of the present national energy situation. Particular emphasis is given to the impact of alternative fuels development on aviation fuels. The future outlook for aircraft fuels is that for the near term, there possibly will be no major fuel changes, but minor specification changes may be possible if supplies decrease. In the midterm, a broad cut fuel may be used if current development efforts are successful. As synfuel production levels increase beyond the 1990's there may be some mixtures of petroleum-based and synfuel products with the possibility of some shale distillate and indirect coal liquefaction products near the year 2000

The diffusion of Mexican immigrants during the 1990s: explanations and impacts

Mexican immigrants were historically clustered in a few cities, mainly in California and Texas. During the past 15 years, however, arrivals from Mexico established sizeable immigrant communities in many “new” cities. We explore the causes and consequences of the widening geographic diffusion of Mexican immigrants. A combination of demand-pull and supply push factors explains most of the inter-city variation in inflows of Mexican immigrants over the 1990s, and also illuminates the most important trend in the destination choices of new Mexican immigrants – the move away from Los Angeles. Mexican inflows raise the relative supply of low-education labor in a city, leading to the question of how cities adapt to these shifts. One mechanism, suggested by the Hecksher Olin model, is shifting industry composition. We find limited evidence of this mechanism: most of the increases in the relative supply of loweducation labor are absorbed by changes in skill intensity within narrowly defined industries. Such adjustments could be readily explained if Mexican immigrant inflows had large effects on the relative wage structures of different cities. As has been found in previous studies of the local impacts of immigration, however, our analysis suggests that relative wage adjustments are small

Skill Biased Technological Change and Rising Wage Inequality: Some Problems and Puzzles

The rise in wage inequality in the U.S. labor market during the 1980s is usually attributed to skill-biased technical change (SBTC), associated with the development of personal computers and related information technologies. We review the evidence in favor of this hypothesis, focusing on the implications of SBTC for economy-wide trends in wage inequality, and for the evolution of wage differentials between various groups. A fundamental problem for the SBTC hypothesis is that wage inequality stabilized in the 1990s, despite continuing advances in computer technology. SBTC also fails to explain the closing of the gender gap, the stability of the racial wage gap, and the dramatic rise in education-related wage gaps for younger versus older workers. We conclude that the SBTC hypothesis is not very helpful in understanding the myriad shifts in the structure of wages that have occurred over the past three decades.

Do Immigrant Inflows Lead to Native Outflows?

We use 1980 and 1990 Census data for 119 larger Metropolitan Statistical Areas to examine the effect of skill-group specific immigrant inflows on the location decisions of natives in the same skill group, and on the overall distribution of human capital. To control for unobserved skill-group specific demand factors, our models include lagged mobility flows of natives over the 1970-80 period. We also estimate instrumental variables models that use the fraction of Mexican immigrants in 1970 to predict skill-group specific relative immigrant inflows over the 1980s. Despite wide variation across cities in the size and relative skill composition of immigrant population changes we find no evidence of selective out-migration by natives. We conclude that immigrant inflows exert a direct effect on the relative skill composition of cities: cities that have received relatively unskilled immigrant flows have experienced proportional rises in the size of their unskilled populations.

Technology and U.S. wage inequality: a brief look

As labor market analysts in the late 1980s and early 1990s documented a rising wage inequality, a series of papers argued that this development was related to rapid technological change. These papers and the large literature that followed established a basis for the virtually unanimous agreement among economists that developments in computers and related information technologies in the 1970s, '80s, and '90s have led to increased wage inequality. ; This view has become known as the "skill-biased technological change" (SBTC) hypothesis-the view that a burst of new technologies increased demand by employers for highly skilled workers (who are more likely to use computers) and that this increased demand led to a rise in the wages of the highly skilled relative to those of the less skilled. ; The authors of this article reconsider the evidence for the SBTC hypothesis and focus on changes over time in overall wage inequality and in the evolution of different groups of workers' relative wages. In doing so, they conclude that SBTC falls far short of unicausal explanation of the substantial changes in the U.S. wage structure of the 1980s and 1990s and does not, by itself, prove to be particularly helpful in organizing or understandings these changes. The article concludes that it is time to re-evaluate the case that SBTC offers a satisfactory explanation for the rise in U.S. wage inequality.Wages ; Productivity ; Technology ; Economic development

Active Labor Market Policy Evaluations: A Meta-analysis

This paper presents a meta-analysis of recent microeconometric evaluations of active labor market policies. Our sample consists of 199 program estimates drawn from 97 studies conducted between 1995 and 2007. In about one-half of these cases we have both a short-term impact estimate (for a one-year post-program horizon) and a medium-term estimate (two-year horizon). We characterize the program estimates according to the type and duration of the program, the characteristics of the participants, and the evaluation methodology. Heterogeneity in all three dimensions affects the likelihood that an impact estimate is significantly positive, significantly negative, or statistically insignificant. Comparing program types, subsidized public sector employment programs have the least favorable impact estimates. Job search assistance programs have relatively favorable short-run impacts, whereas classroom and on-the-job training programs tend to show better outcomes in the medium-run than the short-run. Programs for youths are less likely to yield positive impacts than untargeted programs, but there are no large or systematic differences by gender. Methodologically, we find that the outcome variable used to measure program effectiveness matters. Evaluations based on registered unemployment durations are more likely to show favorable short-term impacts. Controlling for the outcome measure, and the type of program and participants, we find that experimental and non-experimental studies have similar fractions of significant negative and significant positive impact estimates, suggesting that the research designs used in recent non-experimental evaluations are unbiased.

Alphametics for Ten-Digit Squares

Among the nearly 70,000 ten-digit numbers representing the squres of 31, 501 to 99,381, inclusive, only 87 consist of unique digits, i.e., contain all ten digits 0 through 9. A list of these 87 squares is given by T. Charles Jones in the article Squares with 9 and 10 Distinct Digits published on pp. 62-63 of the Journal of Recreational Mathematics 1 (1968). Only 27 of these 87 numbers are the squares of five-digit numbers which likewise consist of unique digits

A Bouquet of Christmas Anagrams

Each line is an anagram of the Christmas message spelled out diagonally in capital letters. Furthermore, the capitalized letters in each line remain in the same positions if the line is re-anagrammed back to the original Christmas message

Eight-Letter Numerical Tautonyms

If letters are assigned values according to their numerical positions in the alphabet (A=1, B=2, etc.), an eight-letter numerical tautonym is a word in which the sum of the values of the first four letters is equal to the sum of the values of the last four letters. For example, B, A, C and K have the numerical values 2, 1, 3 and 11, which sumes to 17, and A, C, H and E have the numerical values 1, 3, 8 and 15, which also sums to 17; thus BACKACHE is a numerical tautonym

Six-Letter Numerical Tautonyms

After reading the article by Darryl Francis on numerical tautonyms in the February 1970 Word Ways, I became interested in the possibility of building one or more word squares consisting of two-part six-letter tautonyms. Since this could not be done with the 45 words listed in his article, I began a systematic search for more, and the list given below is the result