The evolution of employment in Mexico: 1895-1980

Employment figures from the Mexican national census are the basis for this analysis of employment changes in Mexico between 1895-1980. The work identifies longterm trends in the volume and composition of employment and distinguishes 3 main periods in the evolution of employment. The first period, from 1895-1930, marked the end of a stage of development lasting until about 1907 in which sufficient internal stability was achieved to support Mexico's entrance into the world market. Export of agricultural products and metals was the principal focus of economic growth. Construction of roads and railroads was a central element of progress. But economic and social problems manifested in regional disparities, concentration of wealth, conflicts between economic sectors, low pay for agricultural workers, and fierce social and political control characterized the period and culminated in the Mexican Revolution. After the first decade of the 20th century the ability of the economy to absorb new workers began to decline, and the falling of crude activity rates was not reversed until the 1940s. During the 1920s, total employment increased less than 6%, reflecting a net increase of 403,000 male workers and a decrease of 110,000 female workers. The second major period of employment from 1930-1970 saw the change from an economy based on export of primary products to one based on manufacturing for the internal market. There were 2 subperiods, a stage of transition from 1930-50, the economy registered marked fluctuations, but by the 1940s the consolidation of state power and important reforms permitting expansion of the internal market were factors in an accelerated growth of employment relative to the preceding intercensal period. Despite considerable increases in agricultural employment, the relative share of the agricultural sector in total employment was beginning a decline. Employment registered the highest growth rates of the century in the 1940s and exceeded population growth. The increased employment was explained by accelerated growth and accumulation in manufacturing along with increases in commerce, services, construction, and agriculture. From 1950-70, industrial development was consolidated, and there was a generalized expansion in employment in manufacturing as well as in the secondary and tertiary sectors. The economy was less able to absorb new labor, primarily because the agricultural sector had reached the limits of expansion in both the commercial and peasant sector by 1965, at just the time that population growth was most rapid. During the 1970s, manufacturing employment grew less rapidly because of modernization, almost exclusive orientation to the internal market which limited expansion, and scarcity of funds for importing capital goods. A new model of growth will be needed if Mexico is to escape its present stagnation, and a significant share of economic activity will need to be oriented to export. Until this process is consolidated, the national economy is unlikely to show signs of sustained recuperation.     

Growth behavior of the blue blowfly Calliphora vicina maggots

Fifty-three clusters of blowfly eggs of the genus Calliphora vicina were observed in the laboratory up to the hatching stage under reproducible and virtually field-like conditions. Rearing the larvae was then continued up to pupation, the larval growth in length being recorded several times a day. As the object was to study the dependence of the larvae increase in length on the temperature conditions in vitro, the substratal humidity and food supply were kept unchanged during the entire study. The temperature ranged from 6.5 degrees C to 35 degrees C, with the temperature for the individual cluster kept constant during the entire developmental process. Data on about 5500 measured larvae were statistically evaluated. The basic result established was that in the case of the blowfly of the genus Calliphora vicina in vivo, all developmental stages relevant to the entomologic determination of the time of death depend on the temperature conditions: (1) the duration of the egg stage increases with decreasing temperature; (2) the speed of larval growth is slower at lower temperatures; (3) the maximal larval length is reached earlier at higher temperatures; (4) the mean value of maximal length decreases with increasing temperature; (5) larvae under all temperature conditions decrease in size after having reached their maximal length, the decrease in length being more rapid at higher temperatures; (6) constant temperatures over 30 degrees C lead to "stunted forms" which do not pupate and die; (7) constant temperatures under approximately 16 degrees C after the peak of growth has been reached inhibit the readiness to pupate, which causes the larvae to fall into a stationary state of rest, which will be interrupted only when the temperature is raised and resumption of the metamorphosis is thus induced. To allow rapid reconstruction of the larval age in general practice, the established growth data were set out in the form of a diagram designated isomegalendiagram, which permits temperature-fluctuation-related entomologic determination of the time of death with a maximum degree of accuracy.