# Population Growth: Demographic Transition and Malthusian Theories Video

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• 0:01 Population Growth Rate
• 1:34 Malthusian Theory
• 3:09 DTM: 4-Stage Theory
• 8:26 Missing Factors
• 9:15 Lesson Summary
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Lesson Transcript
Instructor: Juli Yelnick

Juli has traveled the world engaging in cultural immersion experiences that bring her Master of Liberal Studies findings to light.

Population growth is not as simple as watching the total number of humans rise each year. This lesson explores how the experts actually calculate population growth rates, and how different theories explain why various regions of the world experience population growth changes in such different ways.

## Understanding Population Growth Rate

As of 2014, the world population has reached over seven billion human inhabitants. This is quite a jump from just 500 years ago, when the world population was likely under one billion. Although the population growth rate is actually down as of 2013, at around 1%, compared to a recent peak of 2.2% in 1963, the overall population of the world continues to increase in sheer numbers.

To understand population growth, we must separate the rate of growth from the total numbers themselves. Even though the world population has continued to rise in number, the rate at which the population is growing has slowed. Most specifically, different populations, or groups of people living in specific areas, around the world have been experiencing shifts in their population growth in very different ways. What accounts for these differences?

Although there are several models for observing and predicting the world's population growth (or shrinkage), one of the most commonly accepted is the demographic transition model (DTM). To calculate population growth, most scholars use the following equation, which captures both natural (birth and death) and mechanical (immigration and emigration) changes in population:

Population Growth Rate (%) = (Births - Deaths) + (Immigrants - Emigrants)

## Malthusian Theory

Malthusian theory is the term used to describe the position of the 19th-century political economist, Reverend Thomas Robert Malthus, in his arguments about how and why population changes. His works, such as An Essay on the Principle of Population, seek to explain the natural pushes and pulls of population fluctuation.

At their core, his arguments remind us that humans are ultimately tied to their environment. Even the most highly developed society can be obliterated by a severe enough drought or plague. Even with the most modern technological advancements in agriculture, Earth will eventually reach its carrying capacity, rendering further population growth impossible.

Malthus' theory consists of principles, the first of which states that human population grows at a geometric rate, or exponentially with each generation. His second principle points to the difference between this geometric rate of growth for human populations and the arithmetic rate of food production, which means that with each generation, the food supply will only increase by the same set number.

For example, although each woman is projected to produce four children, and each of those children will produce four children, the food supply will only increase by two units each generation. According to these first two principles, the population will outgrow the food production capabilities at a certain point in the future.

## Demographic Transition Model (DTM): Four-Stage Theory

A commonly used phrase in the discussion of population growth is demographic transition, which describes a progressive movement from high birth and death rates to low birth and death rates. The demographic transition theory argues that population growth is inextricably tied to a society's level of technology. As the society advances in its usage of technology, in every industry from healthcare to crop production, its birth and death rates shift, directly impacting the population numbers and growth rates.

Stage one of the demographic transition model, or the DTM, is associated with pre-industrial society. In the first stage of human society, birthrate is high and death rate is high, producing a population with a relatively stable size and a slow growth rate. Closely tied to the nature and the limitations of geographical resources, this stage was observable for most of human history.

If the land was fertile that year, then the people were fertile that year. If drought or disease became severe and prolonged, the population shrank. Stage one follows Malthusian theory closely, as it reveals the inherent weakness of a population to thrive beyond the carrying capacity of its natural environment.

Stage two, the next stage, takes place in a developing nation. In the second stage, although the birth rate remains high, the death rate drops, particularly as it applies to infant mortality. Children under five are no longer dying at such high rates, leading to a larger youth population in a given community. This resulting population pyramid, with the large group of youth at the base, reveals a rapidly growing population. This imbalance can be temporary; it occurs as the result of a sudden improvement in the quality of life.

For example, the Industrial Revolution of Western Europe in the mid-1800s led to advances in sanitation, hygiene, and public health initiatives. At the same time, advances in agricultural technology led to higher and more reliable crop yields. As women and children gained access to education and opportunity off the farm, the new urban lifestyle led to a rapid change in population growth. Population growth rates exploded!

Stage three can be seen in a newly developed nation. In the third stage, birthrates drop while death rates remain constant. Attributed to the continued shift in values and lifestyle in the post-Industrial Revolution urban society, women choose to have fewer children. Technology allows for contraception, although it is usually a slow introduction into mainstream usage. More access to health education and more emphasis placed on children remaining in school both contribute to a drop in birthrate.

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