I.	Population Today
II.	Malthus' Times
III.	Malthus' Argument
IV.	Ways to Describe Growth
V.	Malthus' Policy Recommendations and Reactions to Those Recommendations
VI.	How Accurate Was Malthus?
VII.	Websites to Visit:

	Council for the National Institute for the Environment	Links to sources for many environmental issues
	The World Bank	They have the money!
	The United Nations: Economics and Social Development	Sources concerned with sustainable development, needs and rights of the world's least powerful
	United Nations Population Fund	Education, fertility, family planning
	United Nations Population Division	Many population links
	The International Food Policy Research Institute	Trends in subsistence ... and more

I. Population Today
October 12, 1999, was designated "Six Billion Day," the estimated day on which the world's human population hit the six billion mark.

The UN Population Division estimates that, currently, there are 370,000 babies born each day (When a similar lecture was given in 1994, that figure was 266,000.), which amounts to 135 million new people each year, for a net gain of 78 million per year when deaths are taken into account.

There is considerable diversity in population world-wide: China and India contain 2.2 billion, or about 38%, of the 6 billion, while the next most populous country is the United States, which has only 4.6% of the world's population. Next in line are Indonesia, Brazil, Pakistan, and the Russian Federation. Click on Current Population Data for additional information.

Predictions of future growth is somewhat dependent upon the age structure of populations. In what are called the 'developed' nations 20% of the population is 60 years old or older, while in the 'least developed' nations that age group comprises less than 5% of the population. The age structure has many implications for future growth, vitality, social security, crime rates, ... Click on Population Pyramid for a look at examples of age structures.

So, does this all present problems? Well, "experts' differ on that question. For example, Cornell ecologist David Pimentel points out that half the world's people live in poverty, that the Green Revolution, which has provided tremendous growth in grain production for the last forty years, has peaked, and that the amount of arable land is sharply declining. While Steven Mosher of the Population Research Institute points to increasing use of birth control, a declining rate of population growth, and 10 years added to lifespans world-wide. Pimentel says that our finite resources are divided among an increasing number of people and claims that we are heading for a crisis. [USA TODAY, Monday, October 11]

See the Ehrlich & Ehrlich and the Hartmann readings (your Unit III Schedule) for more opposing points of view on the nature of population and human problems.

A way to begin understanding population growth is to look at the person who could be said to have initiated the study by mathematical and, perhaps, scientific means: Thomas Malthus. For, even today, 200 years after he wrote, his ideas form a base and a point of reference (sometimes demonic!) for today's discussions of the population 'problem.'

II. Malthus' Times
Malthus published An Essay on the Principle of Population in 1798 as a thirty-something English minister-political economist. He was aware of much in Europe and the United States; he was ten years old when the American Revolution began and wrote ... The Principle of ... shortly after the French Revolution. He wanted to consider the world as a whole; it is not clear to me how much factual information he had and how much he viewed the world through a lens of English privilege and power. The period in which he lived, called 'The Enlightenment,' was a period of hard times amidst intellectual ferment. There was a belief that human society could not only be improved but perfected and that science could provide a means of doing so.

Malthus had read Adam Smith's The Wealth of Nations, and he was trained in mathematics. So, he had a broad background of mathematics, politics, economics, and theology that he brought to bear upon the problems he saw.

III. Malthus' Argument
Malthus argued that population increases could only, longterm, be stopped by misery and vice, and he based his arguments on two variables: Population and Food. And, he claimed these two variables had two fundamentally different potential growth rates: Geometric and Arithmetic.

He claimed that there was empirical evidence for populations to grow with a fixed amount of time to double. He noted, especially, the land and resource-rich United States, where he claimed that the population doubled every twenty-five years. This fixed doubling time is what is called geometric growth.

In contrast to population growth, he claimed that subsistence, food resources, could at best exhibit arithmetic growth, which means food increasing by a fixed absolute amount in a fixed amount of time.

To see what these two essentially different growths imply, Malthus played out a scenario starting with a population of 7 million (the estimated population of the 'Island,' of England, Scotland, and Wales) and 7 million units of food (enough to just adequately feed the 7 million people). He assumed further that population would double every 25 years and food units would increase by 7 million units every 25 years. Below are the results.

Population	7 million	14 million	28 million	56 million	?	?
Food	7 million	14 million	21 million	28 million	?	?
Year	1800	1825	1850	1875	1900	1925

Looking at the table, things are going along fine for the first 25 years: Food keeps pace with population. But, by 1850 food sources provide only 3/4 of what is just adequate to feed the entire population, and by 1875 only half of the food that is needed.

Note that the geometric growth of population means that for a fixed amount of time there is a fixed proportional increase. In contrast, the arithmetic growth of food units means that for a fixed amount of time there is a fixed absolute amount of increase.

Click here to look at the results graphically. This graph has population and food amounts filled in for times other than 1800, 1825, 1850, etc. The food graph is linear, and it's more common today to describe this kind of growth as linear, rather than arithmetic. The population graph, if properly smoothed out, is exponential, and it's more common today to describe this kind of growth as exponential, rather than geometric.

Malthus' scenario is rather specific, but we can take a look at some variations:

Click here to see the results of starting with 10 million units of food in 1800, but keeping all other assumptions the same.

Click here to see the results of increasing by 14 million units of food in 1800, but keeping all other assumptions the same. The graph is dynamic, so you can adjust the initial amount of food and the increase in food per 25-year period to see the effects. As you increase each amount, look at how much 'time' you are buying - time in which 'misery and vice' is postponed.

In each case, the results are qualitatively the same as in the original scenario: Food may keep up or be more than adequate for a period of time, but eventually population outstrips food only to be checked by misery and vice.

IV. Ways to Describe Growth
There are two ways of describing growth: Absolute and Proportional

Absolute.

Examples of descriptions using absolute growth are:
1. World population is growing by 78 million people per year.
2. It took the world 123 years to go from 1 billion people (1804) to 2 billion people.

Proportional.

Examples of descriptions using proportional growth are:
1. World population was growing at a rate of 2.04% in the late 1960's and is growing at a rate of 1.31% in 1999.
2. Malthus hypothesized a 25-year doubling time.

We look for ways to describe population phenomena so that something is remaining constant, even though we are looking at changing quantities. Malthus believed that there was a constant proportional growth for populations and a constant absolute growth (at best) for food.

Note: It is not obvious, but it is the case that having a constant doubling time is equivalent to having a constant proportional growth rate. The constant 25 year doubling time is the same as a constant 2.8% growth rate. You could check this by taking a number, like 100, and multiplying it by the factor 1.028, then multiply the result by 1.028, and continue in this pattern, keeping track of how many multiplications it takes to get to 200. Similarly, an amount earning an annual 2.8% interest will double in 25 years if the interest is rolled over each year. Below are some equivalences for yearly growth percentages and doubling times, in years.

Yearly Growth Rate	Doubling Time
2.8%	25 yrs
2.04%	34.3 yrs
1.31%	53.3 yrs

V. Malthus Policy Recommendations and Reactions to Those Recommendations
Below are the main recommendations Malthus made (These, and the following reactions to Malthus' policy recommendations, are all, with the exception of the very last quote, taken from the QR reading, An Essay on ... ) to ameliorate conditions of misery:

A. Tillage over pasturage: Grains, legumes to more efficiently feed
B. Agriculture over manufacture: Can't afford to lose sources of food production
C. Moral restraint: Don't have children until you can feed them!
D. Free labor market: People should be free to move about and freely take work wherever it is available.
E. Abolish parish-laws and establish workhouses: Avoid the vicious cycle initiated by public assistance for the poor, which only encourages people to have children beyond their means

A few reactions to ... The Principle of ... from Malthus' contemporaries:

' ... that black and terrible demon that is always ready to stifle the hopes of humanity' - Godwin

' ... this abominable tenet' - Coleridge

' ... this vile and infamous doctrine, this repulsive blasphemy against man and nature' - Engels

' ... Unless Mr. Malthus can contrive to starve someone, he thinks he does nothing' - Hazlitt

And from Betsy Hartmann, one of our contemporaries:

' ... Malthusian alarmists ... There are several reasons why the alarmist message enjoys such credibility. It not only makes good shock headlines in the press, but draws on deep undercurrents of parochialism, racism, and elitism in Western society, complementing the Social Darwinistic 'survival of the fittest' view. The most extreme Malthusians even advocate that famine relief be cut off to the poor overpopulated countries ... '

VI. How Accurate was Malthus?

A few world population facts for the years after Malthus' essay:

Year	World Population
1804	1 billion people	a 123 year doubling time
1927	2 billion people		a 47 year doubling time
1974	4 billion people			a 54 year doubling time
2028 (Projected)	8 billion people

N.B. The Population Institute estimates that 65 countries are on course to double in 30 years or less, and it would be more, if it weren't for AIDS/HIV. Click here to see a graph of world population over the time 1750 - 2050. Note that the period of most rapid growth is in the years 1950 - 2000. For much data in tabular form, click here.

The Green Revolution
In the case of food, biological engineering produced the Green Revolution, which resulted in global cereal production doubling in the period 1960-1990, the period of greatest population growth. During this period, calories per person increased by 35%. The number of undernourished people went from 920 million to 840 million between the late 60's and early 90's.

Click here for more information about food production, past and future, from the International Food Policy Research Institute.