Teaching population dynamics with a simulation exercise

Because many students learn general points best by an empirical demonstration rather than by a purely analytical approach, most of the mysteries of the formation and the evolution of a population under the action of mortality and fertility can be conveniently demonstrated on a computer in the form of population projections under various assumptions. Such an exercise can be simple and yet constitute a powerful teaching tool. Not only will it enable the student to observe the effects of central demographic processes but also it will serve to integrate through concrete applications many of the more technical concepts usually covered in an introductory population course, but rarely made meaningful to average beginning students. An easily administrable exercise along these lines is described in hopes that other instructors in population courses will find it as useful a teaching device as we did.     

Chinese population prospects projection]

Production of population and goods are closely related, mutually restricted, and should be included in our economic plan. Population projection is important in implementation and study of population policy. It is also the foundation of population regulations. Assuming 2 children per couple the population growth rate will be 1% in 1985 and .6% in the year 2000. Therefore, we cannot realize our goal of .5% population growth rate by 1985 and 0% by 2000. A 9% annual growth rate of national production will be required to reach our goal of $1000 U.S. per capita income by the year 2000, a goal that history proves is difficult to achieve. 2 children per couple, therefore, cannot meet our urgent requirements of modernization and educational improvement. A 2nd assumption of 90% single child families after 1 year would yield an average annual population growth rate of .38% in 1985 and .012% in the year 2000. This assumption leads to a rapid population decrease, too rapid for most to accept the change. The 3rd assumption is a gradual increase in single child families to 50% in 1985 and 90% in the year 2000. The resulting growth rates will be .5% in 1983 and near 0% in the year 2000. The projected population boom from 1987 to 1996 will be decreased to an annual increase of .4-.5%. This assumption provides time for people to understand and recognize the importance of the policy. It meets the requirements of modernization and will help improve China's educational and living standards. All 3 assumptions were based on 3 children per couple for minorities.     

Computer simulation study on the cyclicities ofTribolium population dynamics

Summary Under a set of assumptions, a mathematical model was constructed to investigate the effect of cannibalistic behavior and medium renewal schedule onTribolium population dynamics, and the results of simulation analyses were presented to show how modelling can contribute to a better understanding of experimental study. The analyses of the present model, the main concern of which is the cyclicity inTribolium population. showed that there are two distinct factors which create cyclicity, the cannibalistic behavior inTribolium itself, and the medium renewal schedule. Cannibalismper se does not necessarily cause cyclicity, but the combinations of cannibalistic behavior among various life stages and their relative intensities among them can cause cyclicity and can also determine the period of cycle. External factors also can generate cyclicity, but their interaction with cannibalistic behavior has a more significant effect in modifying the period of cycle. Some discrepancies between the model and experimental results were discussed.     

On the rational distribution of Chinese population]

In 1949, the population distribution in China was characterized by the following distinct features. First, it was unbalanced, with high density in the eastern regions, in the plains, and in areas adjacent to railroads, river navigation routes and other transportation axes. Low population density was found in the western regions, mountainous regions, and areas far from transportation routes. Second, Hans were largest in number and distributed throughout the country, with major concentration in the eastern regions, while the minorities constituted about 10% of the total population and were distributed mainly in the far southwestern and northwestern areas. Third, over 89% of the 540 million of the population was distributed in rural areas while only about 10% in towns and cities, with high densities in some coastal cities. During the past 3 decades, the unbalanced nature of China's population has remained basically unchanged. This can be attributed to factors relating to natural conditions and resources, productivities, socioeconomic conditions, and technological development in different regions. In order to achieve a rational distribution of the Chinese population the following measures should be taken: 1) controlling the birth rate of the Hans and increasing the population of minorities; 2) moving the population of the dense areas to the border provinces in the western regions to develop their natural resources and to elevate the living standards; 3) modernizing the rural areas; 4) strictly controlling the industrial developments of large cities and their population growth; and 5) strictly restricting the unplanned migration of population to and from cities.     

The registration of Chinese population in 1982]

The registration of the population is the most crucial part in the entire work of the population census, and it is also the most difficult task. Generally speaking, the population census includes three steps for the complete process: preparations before the census, the practical registration, and the final review. These three steps are closely related to one another, and they form a complete cycle. The preparations before the census include determination of the scope of the census, explanation to the general public of the meaning and significance and demand for the census, preliminary survey of the population situation for the area, and the establishment of registration stations. In the practical registration work, attention should be given to the method, procedure, and principles for the registration. Special arrangements should be made for the popultion who live on boats, move around and live from animal husbandry, and those who belong to ethnic minorities. As for the results of the registration, working staff is required to check and double-check their accuracy. Census regions and different communes should also check on one another's registration in order to correct any possible mistakes. In general, the registration of the populationin the 1982 census was successful, and both the quantity and quality of the registration were improved. This was made possible because of a close cooperation between the people and the government and the hard work by the staff.     

A mathematical model for resource allocation in population programs

The reduction of population growth rates through family planning programs is being attempted in many of the developing nations of the world. This activity lends itself aptly to mathematical modeling. Building from the well-known difference equation model of population growth, a model is constructed which integrates population dynamics, program activities, and resource consumption. The model may be used predictively to assess the outcome of various program activities. Alternatively, it may be used to determine the pattern of activities which yields the greatest reduction in births under the projected resource constraints. A further use of the model is the identification of the parameters to which predictions are most sensitive; such information provides valuable insights to those gathering the input data. The model is here applied to a family planning program currently in progress. An evaluation of the feasibility of that program’s goals is provided, as well as information on limiting resources, data sensitivity, and the most important ages for contraceptive acceptance.     

The effect of the new technological revolution on population dynamics]

The impact of modernization on population dynamics in China is examined. The author notes that the industrialization process involves the concentration of the population in urban areas and the mechanization of agriculture. The need to redistribute the urban population from major urban areas to smaller towns is noted.     

A preliminary discussion of population law]

Population law is basically a kind of social law and it has a system of very rich content. Population law is subject to the influence of both nature and society. Nature has a certain influence and function on the population, including its natural restricting force on the population, such as the life and death cycle, metabolism, and continuation of life. In addition, the natural environment also has a restricting force on the population; people have to live on water, air, sunshine, earth, and other natural resources. People whould have to follow fixed natural laws in order to live, or the continuation of life would be in jeapordy. Society also has some influence on population law and its restriction on the population is mainly through the means of production. On the one hand, it is the function upon the population from the nature, characteristics and condition of productivity. On the other hand, it is the function upon population from production relations. Socialist population law is a major branch of the entire population law. In this particular branch, the main contents include shared individual production and material need and a population development plan which deals with employment, population distribution, and other fundamental problems.     

The prospects of Chinese population growth from 1978 to 2028]

The author presents two alternative projections of the future growth of the Chinese population. The first describes the probable population in 2000 based on official estimates for 1978 and assuming that national population policy goals can be implemented. The second projects population growth for the period 1978-2028 based on the 1978 age composition of the population and average birth and death rates for the period 1973-1978. Two conclusions are drawn. First, the national goal of zero population growth by 2000 will not be reached; at the earliest, the population will cease to grow in 2015. Second, in 2003 and 2028 the young population will greatly outnumber the aged, and in 50 years time half the population will be over 40 years of age.     

A study in miniature of Chinese population

The author analyses the demographic situation of a rural township in West China. He begins by discussing the geographical setting and historical background of the township, pointing out that the bulk of the population is made up of descendants of Hakka immigrants.

In the analysis of the age and sex distribution, special attention is paid to the cultural factors which may affect the reported unequal sex ratio for various age-groups.

In the subsequent discussion, the population of families is classified according to type and size of landholdings and also according to structural family type. The thesis that family size increases with size landholdings is supported by the data for this township and the author presents hypotheses to account for the correlation between large landholdings and large family size. The percentage distribution according to highest educational attainment of the population over six years of age is presented, as well as data which indicate that literacy and educational attainment is lowest for landless workers, increases for landholders with increase in size of holdings, and is highest for merchants and professionals.

The data on which this paper is based were gathered by the author in 1949-50. Population figures collected by local administrators for a 1947 report were reworked and revised through direct investigation and additional material was gathered in detail for the entire population of one representative sub-division of the township; and a random sample of the family heads of that sub-division was singled out for special investigation by means of a structured interview. Such studies in miniature, it is felt, can only suggest hypotheses of wider application; in sufficient number, however, they might provide useful data for China and other countries where modern censuses are still impracticable.     

Akinetic model of population dynamics

The relations between fertility, mortality, growth rate and age distribution in closed populations have been derived by means of a set of differential equations based on the well known theory of chemical kinetics. The classical relations for stable populations are easily obtained in this model by simple algebraic manipulations. A rough but useful further simplification is to divide the population into three groups—pre-reproductive, reproductive, and post-reproductive. For this three-group model simple algebraic expressions connect fertility, mortality, growth rate and the fractions of the population in each group. Although the relations obtained are not precise, they serve to illustrate simply and directly the interactions among the basic population variables.     

非洲的人口动态与分布

非洲的人口动态长期以来具有高出生率、高死亡率的特点,20世纪90年代以后,非洲的人口动态由高出生高死亡模式向高出生中死亡模式转变．死亡率的持续下降在很大程度上是由于数种过去危害最严重的急性传染病基本上得到有效控制的结果。正是死亡率的下降和持续的高出生率导致非洲人口迅速增长。在非洲人口增长的过程中．人口分布是极不平衡的。非洲人口分布的变化与经济因素的人口定期迁移是密切相关的,大致可分为三种情况．这种独特的迁移模式均与经济活动和生产方式直接相关。     

A preliminary analysis of population problems in Taiwan]

Tables are presented to show that Taiwan's mortality rate declined from 18.1 per 1,000 in 1947 to 4.7 per 1,000 in 1976, the birth rate fell from 38.3 per 1,000 in 1947 to 25.9 per 1,000 in 1976, and the rate of natural increase rose from 20.2 in 1947 to 22.2 per 1,000 in 1976. Other tables showing the relationships between population and land use, employment, and medical care are also provided.     

A historical survey of international migration of China population]

Chinese migration trends in various periods of China's history are discussed. From the earliest times to the present, migration patterns seem unique to each period: 1) Early period of emigration (Qin-Tang Dynasties): The earliest recorded instance of emigration occurred during the Qin dynasty when a traveler went to what is now the Philippines. In the following dynasties, even though migration was limited to religious men and merchants who went abroad and returned to China, the process of migrating was established. 2) Tang to Ming Dynasties (Self-initiated migration): Tang Dynasty records show the beginnings of Chinese residence abroad in Arabia. Land and sea travel developed further, and majority of emigres left China for political, religious or economic reasons. 3) Post-Ming Dynasty (Forced migration): This is a period beginning with the Opium War, where 2 groups, indentured servants and those who were able to purchase their own fare, emigrated as laborers because of necessity. The population on the coast, which had risen dramatically by the 1900's, was subject to war, official corruption, poverty and disease. Migration reached a peak between 1851-1875 when 1,280,000 Chinese left the country, settling mostly in Southeast Asia. Between 1847-1873, it is estimated that between 22%-64% perished along the way. 4) WWI-1949 (Motivated migration): The consequences of 2 world wars and the Great Depression were cause for another mass migration from China for political and economic reasons. This time, however, emigres were not limited to the very poor; also, a large number of overseas Chinese eventually returned to the mainland. Between 1930-34, 350,000 more Chinese returned than left. 5) Post-1949 (A new era): In the 1950s large numbers of overseas Chinese returned to the mainland. In 1978-82, over 4000 Chinese returned to Guangdong alone. A new phenomenon has appeared: migration tends to be limited to visits to relatives or to travel for pleasure or education.     

Some general relationships in population dynamics

This paper extends the Lotka system of stable population equations to any population. The authors present this new general system and describe its duality with the recent Preston-Coale system. They derive these results by considering the calculus of change on the surface of population density defined over age and time. They show that analysis of this Lexis surface leads to all the known fundamental relationships of the dynamics of single-region human populations, several interesting new relationships, and a duality between period and cohort life tables.     

A ten-year study of population dynamics of citrus pests in the pesticide-reduced orchard

Summary To determine the effectiveness of a pest management system that uses pesticides at a low level, we censused populations of seven insect pests and three plant diseases from 1980 to 1989 in a citrus orchard which was managed with a pesticide-reduced and pesticide-free protocols, in Wakayama Prefecture, Japan. In the orchard, we controlled the pests solely by spraying petroleum oil once a year from 1980 to 1985, by not spraying insecticide in 1986, and spraying only germicide in 1987. The arrowhead scale population remained much lower level at which citrus trees begin to wither when petroleum oil was sprayed, whereas it rapidly increased and began to wither trees during the years without spraying petroleum oil. The Indian wax scale population rapidly increased only during a 2-year period and then declined. Although the infection level of the sooty mold was unusually high on the trees where the density of the scale was high, this pathogen did little damage to citrus trees. The population of the red wax scale gradually increased throughout the census period but did not reach the level at which citrus trees begin to be damaged. Other pests also caused negligible damages to citrus trees. The results indicated that the pesticide-reduced pest management system which was proposed by Inoue and Ohgushi (1976, 1977) is valid for the prevention of the outbreak of the arrowhead scale, and that is has the sufficient control efficiency for the other pests in citrus orchards. Contribution to the ecological studies of scale insect 3.     

On population of urbanization]

Unlike cities in capitalistic societies our socialistic cities are publically owned, and the relationship between rural and urban areas is mutually supportive and beneficial. 2 types of calculations are required for successful urbanization: an estimate of the total labor required in the city and an estimate of total agricultural products required to support the cities. Disregard for these 2 factors and overpopulated cities will result in unemployment, decreased agricultural production, inflation, and a decreased living standard. A balance between cities and country is important, and therefore population urbanization should be well planned. Capitalistic urbanization of population is based on the principle of private ownership and competition--from unplanned concentration of population in big cities to malignant expansion to the final decline of inner cities. Their governments are forced to redistribute the urban population. The same problem of overpopulated cities in underdeveloped countries results from stagnant agricultural production. We should learn from their mistakes in developing our cities. There are 2 types of socialistic urbanization. Russia has lopsidedly emphasized urban development and ignored agricultural production. Romania, on the other hand, emphasized both labor force distribution and agricultural production. Their numerous small cities near rural areas decrease the difference between big cities and the country. In the past we failed to follow our direction of urbanization--control the size of big cities, reasonably develop mid-sized cities, and actively develop small cities--because of the great difference in living standards between urban and rural areas and the lack of urbanization plans. The concept of industrialization must be accompanied by the concept of population urbanization.     

A preliminary analysis of the present situation of China's population]

The national census conducted in 1982 provides the most up-to-date statistics on China's population. The following are some characteristics of China's population at the present time, based upon preliminary analysis: (1) The total population figure has passed the one billion mark, but the growth rate has been declining since the 1970s; (2) The population density is higher than other countries of the world, but the distribution is uneven. The percentage of the city population is low, and changes in urban and rural distribution are slow; (3) The population growth of ethnic minorities is higher than average, and the ratio of the minority population is increasing; (4) There are slightly more men than women-an impact of traditional society; (5) The age structure of the population is still young, but sharp change is in the process of developing; (6) Fertility has declined on a large scale, but is still far from reaching the goal of population control; (7) The death rate has remained at a low level for a long period of time, and average lifespan is gradually becoming prolonged; (8) The marital status has remained stable, and people normally marry between the ages of 20 and 30; (9) The cultural and educational level of the general public has been promoted, but still not enough for modernized construction; (10) The employment rate is high, and most of the working population is employed with the departments of material production. The percentage of employment of a service nature is small. A high percentage of the working population is related to agriculture, fishing, and animal husbandry. The precentage of workers in manual labor is much higher than that for mental labor.     

A preliminary analysis of negative population growth in Taicang County]

This report attempts to analyze the negative population growth and its significance in Tai-Cang County, China. Based on population data provided by local Tai-Cang authorities, family planning effectively lowered the birth rate from 11.9% between 1960-1969 to 3.0% between 1979-1983. The rate of single-child families grew enormously while the number of 2-child families reached a record low. Families with more than 2 children virtually vanished by 1983. Moreover, while a younger marriage age in 1981 and 1982 contributed to a slight increase in the birth rate, new marriage laws in 1983 caused an older marriage age and acted to lower the birth rate due to the fact that mothers were bearing children at an older age. A change in population components also influenced this low birth rate: the county population below the age of 14 is 21.2% compared with 33.6% nationally; however, the percentage of the population in this county over the age of 65 is 8.5% while the national figure is 4.9%. Finally, the marriagable population of females (i.e., 23 years old) was slightly lower between 1982-1984 due to the low birth rate seen from 1959-1961. The findings indicate that family planning is effective in lowering birth rates along with late marriages and older childbearing ages. The negative population growth in Tai-Cang County, however, is a temporary phenomenon. The indications are that the problems and shortcomings of family planning must be overcome, regional population planning must be improved, and the study of eugenics and optimum population reinforced. The report also notes that the population trend is toward aging.     

A study of urban population migration and urbanization in China]

Under the auspices of the Chinese Academy of Social Sciences and UN funding, a study was undertaken to assess Chinese urban migration and urbanization. A 2% random sample was taken of 74 cities of varying densities (divided into 5 categories ranging from "especially large city" to "town") from 16 provinces. This encompassed 23,895 households, 1,643 collectives and 100,167 people. Major data include: 38% of the subjects had migrated at least once; 7.58% lived away from home for at least 1 year; 23.98% were temporarily away from home at the time of the study; 3.6% were at home. With the exception of the "especially large city," which absorbed 46.5% of urban migrants, more migrants entered "towns" than they did "large city." Migration to the "especially large city" fell from 56.6% in the 1950s to 32.5% between 1981-86, whereas migration into the other categories increased. For example, population movement into towns jumped from 12.3% in the 1950s to 28.6% in 1981-86. In all 5 categories, intra-province migration was larger than inter-province migration. Over half of the urban migrants moved from villages to towns. More men migrated to cities than women, but slightly more women than men migrated from villages to cities (due to marriage customs). 56.6% of migrants were between 15-30 years; 23.34% were workers; 21.54% were farmers. Reasons given for moving were many, but the most often cited was work related. Work related moves often meant that such migration was dictated, rather than voluntary. Also, social, economic and political upheavals directly affected the pattern of urban migration from 1949-86. Current government policy is to develop smaller cities and to limit the growth of already densely populated areas. Until cities can provide adequate housing, food and jobs for its inhabitants, governmental intervention in some areas will continue to be necessary.