|
Eating Fossil Fuels
Author: Dale Allen Pfeiffer
[Some months ago, concerned by a Paris statement made by Professor
Kenneth Deffeyes of Princeton regarding his concern about the impact of
Peak Oil and Gas on fertilizer production, I tasked FTW's Contributing
Editor for Energy, Dale Allen Pfeiffer to start looking into what
natural gas shortages would do to fertilizer production costs. His
investigation led him to look at the totality of food production in the
US. Because the US and Canada feed much of the world, the answers have
global implications.
What follows is most certainly the single most frightening article I
have ever read and certainly the most alarming piece that FTW has ever
published. Even as we have seen CNN, Britain's Independent and Jane's
Defence Weekly acknowledge the reality of Peak Oil and Gas within the
last week, acknowledging that world oil and gas reserves are as much as
80% less than predicted, we are also seeing how little real thinking
has been devoted to the host of crises certain to follow; at least in
terms of publicly accessible thinking.
The following article is so serious in its implications that I have
taken the unusual step of underlining some of its key findings. I did
that with the intent that the reader treat each underlined passage as a
separate and incredibly important fact. Each one of these facts should
be read and digested separately to assimilate its importance. I found
myself reading one fact and then getting up and walking away until I
could come back and (un)comfortably read to the next.
All told, Dale Allen Pfeiffer's research and reporting confirms the
worst of FTW's suspicions about the consequences of Peak Oil, and it
poses serious questions about what to do next. Not the least of these
is why, in a presidential election year, none of the candidates has
even acknowledged the problem. Thus far, it is clear that solutions for
these questions, perhaps the most important ones facing mankind, will
by necessity be found by private individuals and communities,
independently of outside or governmental help. Whether the real search
for answers comes now, or as the crisis becomes unavoidable, depends
solely on us. - MCR]
October 3 , 2003, 1200 PDT, (FTW) -- Human beings (like all other
animals) draw their energy from the food they eat. Until the last
century, all of the food energy available on this planet was derived
from the sun through photosynthesis. Either you ate plants or you ate
animals that fed on plants, but the energy in your food was ultimately
derived from the sun.
It would have been absurd to think that we would one day run out of
sunshine. No, sunshine was an abundant, renewable resource, and the
process of photosynthesis fed all life on this planet. It also set a
limit on the amount of food that could be generated at any one time,
and therefore placed a limit upon population growth. Solar energy has a
limited rate of flow into this planet. To increase your food
production, you had to increase the acreage under cultivation, and
displace your competitors. There was no other way to increase the
amount of energy available for food production. Human population grew
by displacing everything else and appropriating more and more of the
available solar energy.
The need to expand agricultural production was one of the motive causes
behind most of the wars in recorded history, along with expansion of
the energy base (and agricultural production is truly an essential
portion of the energy base). And when Europeans could no longer expand
cultivation, they began the task of conquering the world. Explorers
were followed by conquistadors and traders and settlers. The declared
reasons for expansion may have been trade, avarice, empire or simply
curiosity, but at its base, it was all about the expansion of
agricultural productivity. Wherever explorers and conquistadors
traveled, they may have carried off loot, but they left plantations.
And settlers toiled to clear land and establish their own homestead.
This conquest and expansion went on until there was no place left for
further expansion. Certainly, to this day, landowners and farmers fight
to claim still more land for agricultural productivity, but they are
fighting over crumbs. Today, virtually all of the productive land on
this planet is being exploited by agriculture. What remains unused is
too steep, too wet, too dry or lacking in soil nutrients.1
Just when agricultural output could expand no more by increasing
acreage, new innovations made possible a more thorough exploitation of
the acreage already available. The process of "pest" displacement and
appropriation for agriculture accelerated with the industrial
revolution as the mechanization of agriculture hastened the clearing
and tilling of land and augmented the amount of farmland which could be
tended by one person. With every increase in food production, the human
population grew apace.
At present, nearly 40% of all land-based photosynthetic capability has
been appropriated by human beings.2 In the United States we divert more
than half of the energy captured by photosynthesis.3 We have taken over
all the prime real estate on this planet. The rest of nature is forced
to make due with what is left. Plainly, this is one of the major
factors in species extinctions and in ecosystem stress.
The Green Revolution
In the 1950s and 1960s, agriculture underwent a drastic transformation
commonly referred to as the Green Revolution. The Green Revolution
resulted in the industrialization of agriculture. Part of the advance
resulted from new hybrid food plants, leading to more productive food
crops. Between 1950 and 1984, as the Green Revolution transformed
agriculture around the globe, world grain production increased by
250%.4 That is a tremendous increase in the amount of food energy
available for human consumption. This additional energy did not come
from an increase in incipient sunlight, nor did it result from
introducing agriculture to new vistas of land. The energy for the Green
Revolution was provided by fossil fuels in the form of fertilizers
(natural gas), pesticides (oil), and hydrocarbon fueled irrigation.
The Green Revolution increased the energy flow to agriculture by an
average of 50 times the energy input of traditional agriculture.5 In
the most extreme cases, energy consumption by agriculture has increased
100 fold or more.6
In the United States, 400 gallons of oil equivalents are expended
annually to feed each American (as of data provided in 1994).7
Agricultural energy consumption is broken down as follows:
* 31% for the manufacture of inorganic
fertilizer
* 19% for the operation of field
machinery
* 16% for transportation
* 13% for irrigation
* 08% for raising livestock (not
including livestock feed)
* 05% for crop drying
* 05% for pesticide production
* 08% miscellaneous8
Energy costs for packaging, refrigeration, transportation to retail
outlets, and household cooking are not considered in these figures.
To give the reader an idea of the energy intensiveness of modern
agriculture, production of one kilogram of nitrogen for fertilizer
requires the energy equivalent of from 1.4 to 1.8 liters of diesel
fuel. This is not considering the natural gas feedstock.9 According to
The Fertilizer Institute (http://www.tfi.org), in the year from June 30
2001 until June 30 2002 the United States used 12,009,300 short tons of
nitrogen fertilizer.10 Using the low figure of 1.4 liters diesel
equivalent per kilogram of nitrogen, this equates to the energy content
of 15.3 billion liters of diesel fuel, or 96.2 million barrels.
Of course, this is only a rough comparison to aid comprehension of the
energy requirements for modern agriculture.
In a very real sense, we are literally eating fossil fuels. However,
due to the laws of thermodynamics, there is not a direct correspondence
between energy inflow and outflow in agriculture. Along the way, there
is a marked energy loss. Between 1945 and 1994, energy input to
agriculture increased 4-fold while crop yields only increased 3-fold.11
Since then, energy input has continued to increase without a
corresponding increase in crop yield. We have reached the point of
marginal returns. Yet, due to soil degradation, increased demands of
pest management and increasing energy costs for irrigation (all of
which is examined below), modern agriculture must continue increasing
its energy expenditures simply to maintain current crop yields. The
Green Revolution is becoming bankrupt.
Fossil Fuel Costs
Solar energy is a renewable resource limited only by the inflow rate
from the sun to the earth. Fossil fuels, on the other hand, are a
stock-type resource that can be exploited at a nearly limitless rate.
However, on a human timescale, fossil fuels are nonrenewable. They
represent a planetary energy deposit which we can draw from at any rate
we wish, but which will eventually be exhausted without renewal. The
Green Revolution tapped into this energy deposit and used it to
increase agricultural production.
Total fossil fuel use in the United States has increased 20-fold in the
last 4 decades. In the US, we consume 20 to 30 times more fossil fuel
energy per capita than people in developing nations. Agriculture
directly accounts for 17% of all the energy used in this country.12 As
of 1990, we were using approximately 1,000 liters (6.41 barrels) of oil
to produce food of one hectare of land.13
In 1994, David Pimentel and Mario Giampietro estimated the output/input
ratio of agriculture to be around 1.4.14 For 0.7 Kilogram-Calories
(kcal) of fossil energy consumed, U.S. agriculture produced 1 kcal of
food. The input figure for this ratio was based on FAO (Food and
Agriculture Organization of the UN) statistics, which consider only
fertilizers (without including fertilizer feedstock), irrigation,
pesticides (without including pesticide feedstock), and machinery and
fuel for field operations. Other agricultural energy inputs not
considered were energy and machinery for drying crops, transportation
for inputs and outputs to and from the farm, electricity, and
construction and maintenance of farm buildings and infrastructures.
Adding in estimates for these energy costs brought the input/output
energy ratio down to 1.15 Yet this does not include the energy expense
of packaging, delivery to retail outlets, refrigeration or household
cooking.
In a subsequent study completed later that same year (1994), Giampietro
and Pimentel managed to derive a more accurate ratio of the net fossil
fuel energy ratio of agriculture.16 In this study, the authors defined
two separate forms of energy input: Endosomatic energy and Exosomatic
energy. Endosomatic energy is generated through the metabolic
transformation of food energy into muscle energy in the human body.
Exosomatic energy is generated by transforming energy outside of the
human body, such as burning gasoline in a tractor. This assessment
allowed the authors to look at fossil fuel input alone and in ratio to
other inputs.
Prior to the industrial revolution, virtually 100% of both endosomatic
and exosomatic energy was solar driven. Fossil fuels now represent 90%
of the exosomatic energy used in the United States and other developed
countries.17 The typical exo/endo ratio of pre-industrial, solar
powered societies is about 4 to 1. The ratio has changed tenfold in
developed countries, climbing to 40 to 1. And in the United States it
is more than 90 to 1.18 The nature of the way we use endosomatic energy
has changed as well.
The vast majority of endosomatic energy is no longer expended to
deliver power for direct economic processes. Now the majority of
endosomatic energy is utilized to generate the flow of information
directing the flow of exosomatic energy driving machines. Considering
the 90/1 exo/endo ratio in the United States, each endosomatic kcal of
energy expended in the US induces the circulation of 90 kcal of
exosomatic energy. As an example, a small gasoline engine can convert
the 38,000 kcal in one gallon of gasoline into 8.8 KWh (Kilowatt
hours), which equates to about 3 weeks of work for one human being.19
In their refined study, Giampietro and Pimentel found that 10 kcal of
exosomatic energy are required to produce 1 kcal of food delivered to
the consumer in the U.S. food system. This includes packaging and all
delivery expenses, but excludes household cooking).20 The U.S. food
system consumes ten times more energy than it produces in food energy.
This disparity is made possible by nonrenewable fossil fuel stocks.
Assuming a figure of 2,500 kcal per capita for the daily diet in the
United States, the 10/1 ratio translates into a cost of 35,000 kcal of
exosomatic energy per capita each day. However, considering that the
average return on one hour of endosomatic labor in the U.S. is about
100,000 kcal of exosomatic energy, the flow of exosomatic energy
required to supply the daily diet is achieved in only 20 minutes of
labor in our current system. Unfortunately, if you remove fossil fuels
from the equation, the daily diet will require 111 hours of endosomatic
labor per capita; that is, the current U.S. daily diet would require
nearly three weeks of labor per capita to produce.
Quite plainly, as fossil fuel production begins to decline within the
next decade, there will be less energy available for the production of
food.
Soil, Cropland and Water
Modern intensive agriculture is unsustainable. Technologically-enhanced
agriculture has augmented soil erosion, polluted and overdrawn
groundwater and surface water, and even (largely due to increased
pesticide use) caused serious public health and environmental problems.
Soil erosion, overtaxed cropland and water resource overdraft in turn
lead to even greater use of fossil fuels and hydrocarbon products. More
hydrocarbon-based fertilizers must be applied, along with more
pesticides; irrigation water requires more energy to pump; and fossil
fuels are used to process polluted water.
It takes 500 years to replace 1 inch of topsoil.21 In a natural
environment, topsoil is built up by decaying plant matter and
weathering rock, and it is protected from erosion by growing plants. In
soil made susceptible by agriculture, erosion is reducing productivity
up to 65% each year.22 Former prairie lands, which constitute the bread
basket of the United States, have lost one half of their topsoil after
farming for about 100 years. This soil is eroding 30 times faster than
the natural formation rate.23 Food crops are much hungrier than the
natural grasses that once covered the Great Plains. As a result, the
remaining topsoil is increasingly depleted of nutrients. Soil erosion
and mineral depletion removes about $20 billion worth of plant
nutrients from U.S. agricultural soils every year.24 Much of the soil
in the Great Plains is little more than a sponge into which we must
pour hydrocarbon-based fertilizers in order to produce crops.
Every year in the U.S., more than 2 million acres of cropland are lost
to erosion, salinization and water logging. On top of this,
urbanization, road building, and industry claim another 1 million acres
annually from farmland.24 Approximately three-quarters of the land area
in the United States is devoted to agriculture and commercial
forestry.25 The expanding human population is putting increasing
pressure on land availability. Incidentally, only a small portion of
U.S. land area remains available for the solar energy technologies
necessary to support a solar energy-based economy. The land area for
harvesting biomass is likewise limited. For this reason, the
development of solar energy or biomass must be at the expense of
agriculture.
Modern agriculture also places a strain on our water resources.
Agriculture consumes fully 85% of all U.S. freshwater resources.26
Overdraft is occurring from many surface water resources, especially in
the west and south. The typical example is the Colorado River, which is
diverted to a trickle by the time it reaches the Pacific. Yet surface
water only supplies 60% of the water used in irrigation. The remainder,
and in some places the majority of water for irrigation, comes from
ground water aquifers. Ground water is recharged slowly by the
percolation of rainwater through the earth's crust. Less than 0.1% of
the stored ground water mined annually is replaced by rainfall.27 The
great Ogallala aquifer that supplies agriculture, industry and home use
in much of the southern and central plains states has an annual
overdraft up to 160% above its recharge rate. The Ogallala aquifer will
become unproductive in a matter of decades.28
We can illustrate the demand that modern agriculture places on water
resources by looking at a farmland producing corn. A corn crop that
produces 118 bushels/acre/year requires more than 500,000 gallons/acre
of water during the growing season. The production of 1 pound of maize
requires 1,400 pounds (or 175 gallons) of water.29 Unless something is
done to lower these consumption rates, modern agriculture will help to
propel the United States into a water crisis.
In the last two decades, the use of hydrocarbon-based pesticides in the
U.S. has increased 33-fold, yet each year we lose more crops to
pests.30 This is the result of the abandonment of traditional crop
rotation practices. Nearly 50% of U.S. corn land is grown continuously
as a monoculture.31 This results in an increase in corn pests, which in
turn requires the use of more pesticides. Pesticide use on corn crops
had increased 1,000-fold even before the introduction of genetically
engineered, pesticide resistant corn. However, corn losses have still
risen 4-fold.32
Modern intensive agriculture is unsustainable. It is damaging the land,
draining water supplies and polluting the environment. And all of this
requires more and more fossil fuel input to pump irrigation water, to
replace nutrients, to provide pest protection, to remediate the
environment and simply to hold crop production at a constant. Yet this
necessary fossil fuel input is going to crash headlong into declining
fossil fuel production.
US Consumption
In the United States, each person consumes an average of 2,175 pounds
of food per person per year. This provides the U.S. consumer with an
average daily energy intake of 3,600 Calories. The world average is
2,700 Calories per day.33 Fully 19% of the U.S. caloric intake comes
from fast food. Fast food accounts for 34% of the total food
consumption for the average U.S. citizen. The average citizen dines out
for one meal out of four.34
One third of the caloric intake of the average American comes from
animal sources (including dairy products), totaling 800 pounds per
person per year. This diet means that U.S. citizens derive 40% of their
calories from fat-nearly half of their diet.35
Americans are also grand consumers of water. As of one decade ago,
Americans were consuming 1,450 gallons/day/capita (g/d/c), with the
largest amount expended on agriculture. Allowing for projected
population increase, consumption by 2050 is projected at 700 g/d/c,
which hydrologists consider to be minimal for human needs.36 This is
without taking into consideration declining fossil fuel production.
To provide all of this food requires the application of 0.6 million
metric tons of pesticides in North America per year. This is over one
fifth of the total annual world pesticide use, estimated at 2.5 million
tons.37 Worldwide, more nitrogen fertilizer is used per year than can
be supplied through natural sources. Likewise, water is pumped out of
underground aquifers at a much higher rate than it is recharged. And
stocks of important minerals, such as phosphorus and potassium, are
quickly approaching exhaustion.38
Total U.S. energy consumption is more than three times the amount of
solar energy harvested as crop and forest products. The United States
consumes 40% more energy annually than the total amount of solar energy
captured yearly by all U.S. plant biomass. Per capita use of fossil
energy in North America is five times the world average.39
Our prosperity is built on the principal of exhausting the world's
resources as quickly as possible, without any thought to our neighbors,
all the other life on this planet, or our children.
Population & Sustainability
Considering a growth rate of 1.1% per year, the U.S. population is
projected to double by 2050. As the population expands, an estimated
one acre of land will be lost for every person added to the U.S.
population. Currently, there are 1.8 acres of farmland available to
grow food for each U.S. citizen. By 2050, this will decrease to 0.6
acres. 1.2 acres per person is required in order to maintain current
dietary standards.40
Presently, only two nations on the planet are major exporters of grain:
the United States and Canada.41 By 2025, it is expected that the U.S.
will cease to be a food exporter due to domestic demand. The impact on
the U.S. economy could be devastating, as food exports earn $40 billion
for the U.S. annually. More importantly, millions of people around the
world could starve to death without U.S. food exports.42
Domestically, 34.6 million people are living in poverty as of 2002
census data.43 And this number is continuing to grow at an alarming
rate. Too many of these people do not have a sufficient diet. As the
situation worsens, this number will increase and the United States will
witness growing numbers of starvation fatalities.
There are some things that we can do to at least alleviate this
tragedy. It is suggested that streamlining agriculture to get rid of
losses, waste and mismanagement might cut the energy inputs for food
production by up to one-half.35 In place of fossil fuel-based
fertilizers, we could utilize livestock manures that are now wasted. It
is estimated that livestock manures contain 5 times the amount of
fertilizer currently used each year.36 Perhaps most effective would be
to eliminate meat from our diet altogether.37
Mario Giampietro and David Pimentel postulate that a sustainable food
system is possible only if four conditions are met:
1. Environmentally sound agricultural technologies
must be implemented.
2. Renewable energy technologies must be put into
place.
3. Major increases in energy efficiency must
reduce exosomatic energy consumption per capita.
4. Population size and consumption must be
compatible with maintaining the stability of environmental processes.38
Providing that the first three conditions are met, with a reduction to
less than half of the exosomatic energy consumption per capita, the
authors place the maximum population for a sustainable economy at 200
million.39 Several other studies have produced figures within this
ballpark (Energy and Population, Werbos, Paul J.
http://www.dieoff.com/page63.htm; Impact of Population Growth on Food
Supplies and Environment, Pimentel, David, et al.
http://www.dieoff.com/page57.htm).
Given that the current U.S. population is in excess of 292 million, 40
that would mean a reduction of 92 million. To achieve a sustainable
economy and avert disaster, the United States must reduce its
population by at least one-third. The black plague during the 14th
Century claimed approximately one-third of the European population (and
more than half of the Asian and Indian populations), plunging the
continent into a darkness from which it took them nearly two centuries
to emerge.41
None of this research considers the impact of declining fossil fuel
production. The authors of all of these studies believe that the
mentioned agricultural crisis will only begin to impact us after 2020,
and will not become critical until 2050. The current peaking of global
oil production (and subsequent decline of production), along with the
peak of North American natural gas production will very likely
precipitate this agricultural crisis much sooner than expected. Quite
possibly, a U.S. population reduction of one-third will not be
effective for sustainability; the necessary reduction might be in
excess of one-half. And, for sustainability, global population will
have to be reduced from the current 6.32 billion people42 to 2
billion-a reduction of 68% or over two-thirds. The end of this decade
could see spiraling food prices without relief. And the coming decade
could see massive starvation on a global level such as never
experienced before by the human race.
Three Choices
Considering the utter necessity of population reduction, there are
three obvious choices awaiting us.
We can-as a society-become aware of our dilemma and consciously make
the choice not to add more people to our population. This would be the
most welcome of our three options, to choose consciously and with free
will to responsibly lower our population. However, this flies in the
face of our biological imperative to procreate. It is further
complicated by the ability of modern medicine to extend our longevity,
and by the refusal of the Religious Right to consider issues of
population management. And then, there is a strong business lobby to
maintain a high immigration rate in order to hold down the cost of
labor. Though this is probably our best choice, it is the option least
likely to be chosen.
Failing to responsibly lower our population, we can force population
cuts through government regulations. Is there any need to mention how
distasteful this option would be? How many of us would choose to live
in a world of forced sterilization and population quotas enforced under
penalty of law? How easily might this lead to a culling of the
population utilizing principles of eugenics?
This leaves the third choice, which itself presents an unspeakable
picture of suffering and death. Should we fail to acknowledge this
coming crisis and determine to deal with it, we will be faced with a
die-off from which civilization may very possibly never revive. We will
very likely lose more than the numbers necessary for sustainability.
Under a die-off scenario, conditions will deteriorate so badly that the
surviving human population would be a negligible fraction of the
present population. And those survivors would suffer from the trauma of
living through the death of their civilization, their neighbors, their
friends and their families. Those survivors will have seen their world
crushed into nothing.
The questions we must ask ourselves now are, how can we allow this to
happen, and what can we do to prevent it? Does our present lifestyle
mean so much to us that we would subject ourselves and our children to
this fast approaching tragedy simply for a few more years of
conspicuous consumption?
Author's Note
This is possibly the most important article I have written to date. It
is certainly the most frightening, and the conclusion is the bleakest I
have ever penned. This article is likely to greatly disturb the reader;
it has certainly disturbed me. However, it is important for our future
that this paper should be read, acknowledged and discussed.
I am by nature positive and optimistic. In spite of this article, I
continue to believe that we can find a positive solution to the
multiple crises bearing down upon us. Though this article may provoke a
flood of hate mail, it is simply a factual report of data and the
obvious conclusions that follow from it.
Endnotes
| 1. |
Availability
of agricultural land for crop
and livestock production, Buringh,
P. Food and Natural Resources,
Pimentel. D. and Hall. C.W. (eds),
Academic Press, 1989. |
| 2. |
Human
appropriation of the products
of photosynthesis, Vitousek, P.M.
et al. Bioscience 36, 1986. http://www.science.duq.edu/esm/unit2-3 |
| 3. |
Land,
Energy and Water: the constraints
governing Ideal US Population
Size, Pimental, David and Pimentel,
Marcia. Focus, Spring 1991. NPG
Forum, 1990. http://www.dieoff.com/page136.htm |
| 4. |
Constraints
on the Expansion of Global Food
Supply, Kindell, Henry H. and
Pimentel, David. Ambio Vol. 23
No. 3, May 1994. The Royal Swedish
Academy of Sciences. http://www.dieoff.com/page36htm |
| 5. |
The
Tightening Conflict: Population,
Energy Use, and the Ecology of
Agriculture, Giampietro, Mario
and Pimentel, David, 1994. http://www.dieoff.com/page69.htm |
| 6. |
Op.
Cit. See note 4. |
| 7. |
Food,
Land, Population and the U.S.
Economy, Pimentel, David and Giampietro,
Mario. Carrying Capacity Network,
11/21/1994. http://www.dieoff.com/page55.htm |
| 8. |
Comparison
of energy inputs for inorganic
fertilizer and manure based corn
production, McLaughlin, N.B.,
et al. Canadian Agricultural Engineering,
Vol. 42, No. 1, 2000. |
| 9. |
Ibid. |
| 10. |
US
Fertilizer Use Statistics. http://www.tfi.org/Statistics/USfertuse2.asp |
| 11. |
Food,
Land, Population and the U.S.
Economy, Executive Summary, Pimentel,
David and Giampietro, Mario. Carrying
Capacity Network, 11/21/1994.
http://www.dieoff.com/page40.htm |
| 12. |
Ibid. |
| 13. |
Op.
Cit. See note 3. |
| 14. |
Op.
Cit. See note 7. |
| 15. |
Ibid. |
| 16. |
Op.
Cit. See note 5. |
| 17. |
Ibid. |
| 18. |
Ibid. |
| 19. |
Ibid. |
| 20. |
Ibid. |
| 21. |
Op.
Cit. See note 11. |
| 22. |
Ibid. |
| 23. |
Ibid. |
| 24 |
Ibid. |
| 25. |
Op
Cit. See note 3. |
| 26. |
Op
Cit. See note 11. |
| 27. |
Ibid. |
| 28. |
Ibid. |
| 29. |
Ibid. |
| 30. |
Op
Cit. See note 3. |
| 31. |
Op
Cit. See note 5. |
| 32. |
Op
Cit. See note 3. |
| 33. |
Op
Cit. See note 11. |
| 34. |
Food
Consumption and Access, Lynn Brantley,
et al. Capital Area Food Bank,
6/1/2001. http://www.clagettfarm.org/purchasing.html |
| 35. |
Op
Cit. See note 11. |
| 36. |
Ibid. |
| 37. |
Op
Cit. See note 5. |
| 38. |
Ibid. |
| 39. |
Ibid. |
| 40 |
Op
Cit. See note 11. |
| 41 |
Op
Cit. See note 4. |
| 42. |
Op
Cit. See note 1. |
| 43. |
Poverty
2002. The U.S. Census Bureau.
http://www.census.gov/hhes/poverty/poverty02/pov02hi.html |
|
|
