Population change

Human population change is the difference between the size of the population from the beginning to the end of a certain time period. In other words, population change refers to change in the number of people during a specific time period. As a whole,the world population has not been stable; it has increased manifold. Due to this constant changing population, the subject of demographics, the statistics of how many people there are in a given population, was created. Demography can also be defined as the study of populations, and the factors that cause the most amount of population growth or decline. The main measurements of demography include: birth rates, death rates, sex ratios, life expectancy, and migration rates. All of these measures are found by a series of surveys and censuses conducted over a time period in order to compare how the population is changing.^[1] Other ways to measure population demographics include the use of historical maps, aerial photographs, and census statistics.^[2] One of the reasons why demographers use statistics about population change is because of the social and demographic transformations that the world experiences; significant challenges for the government and businesses will take effect depending on the degree of the population change.^[3]

The most common way to calculate population change is to exam the births and deaths in a population. The number of births and deaths is directly related to how fast the population is growing, as well as how long the people will live. For a long period of time, the world's population grew steadily but slowly. Large numbers of babies were born but died early due to various causes such as insufficient health facilities, and the lack of food available. Farmers were not able to produce enough to meet the food requirements for the growing population, causing many deaths. As a result of this, the total increase in population was very low. However, due to recent growth in technology, education, and medical care, the worlds population has grown exponentially. The natural resources that were once scarce are now being mass-produced. Because of this change, many countries are setting into place policies to help control the growing population. Some of these policies include: better health care, education, and birth limitations.^[4] As the population size begins to grow, the life expectancy has changed as a result. This started with a rapid decrease in deaths, followed by a slight increase in fertility, causing a boom in aging people. Soon after, fertility began to decline, causing the population to grow faster and older, leading to total population increase over time.^[5] One of the biological reasons for the fertility decline is because of chromosome segregation during cell division that behave abnormally in older eggs.^[6] Other reasons like more women in the workforce also explain the fertility decline over the years. Recent studies also show that there has been a decline in fertility from the ages 25 to 29, which is surprising because this age group had the highest birth rates in the past.^[7] The birth rate percentages over the age of 30 and under the age of 30 are also varying in the sense that there is more drop in birthrates of women under the age of 30 than women over the age of 30.^[7]

The best way to visualize the population change phenomenon is to exam population pyramids. Population pyramids are set up to examine how many people per gender are in a certain age bracket.^[8] However, this visual example of each population raises questions on how countries compare to each other. Many countries have differently shaped population pyramids which caused demographers to investigate. Population pyramid shape is due to the internal issues of a population such as: access to education, health care, industrialization, and access to natural resources.^[9] Another factor that affects population and how we calculate it are Tempo Effects. Tempo Effects are a wide arrange of phenomenon that can effect demographics and fertility rates.^[10] An example of a Tempo Effect could be war (such as the civil war) or genocide (such as the Holocaust.) Tempo Effects can be looked at as forced changes in population but there are also errors in the census that can affect the population as well. There have been known errors in the census from country to country which lead to more inaccurate population pyramids. Errors include coverage errors in the census in the less developed countries as well as content errors from responses by those answering the question. Errors can lead to a lack of resources for a particular area which can lead to an increase in mortality as well as a drop in fertility. In addition, funding for areas would not be enough to sustain living if their count is not accurate due to error. As of Monday, March 26, 2018, the Trump Administration has added a new question to the Census: Are you a citizen? Whether or not this is looked at negatively or positively it will change populations according to the Census Bureau.^[11] Based on this knowledge, countries can be analyzed to see what areas they are thriving in versus lagging in. Population pyramids also show how fast a country is growing based on their shape. A country with a wider base and a smaller top, reflecting a triangle shape, will be growing more rapidly than a population that is shaped like a rectangle.^[9] Examples of population pyramids by year can be found here.

References

• Explaining population change, from the European statistics.