“Take-Back” Principle—The belief that manufac-
turers of products should have the responsibility
to take the packaging and the products back at
the end of their useful lives in order to promote
efficient packaging and recycling. (Also called
extended producer responsibility.)
Tangible Benefits—Benefits that can reasonably be
assigned a monetary value.
Technological Progress—An innovation in process
or technique that allows more output or services
to be derived from a given set of inputs.
Theory of Demographic Transition—A theory
that shows how population growth is related to
the stages of industrial development.
Thermal Pollution—Pollution caused by the injec-
tion of heat into a watercourse.
Third Parties—Victims who have no contractual
relationship to a pollution source. (They are nei-
ther consumers of the product produced by the
source nor employed by the source.)
Total Cost—The sum of fixed and variable costs.
Total Fertility Rate—The number of live births an
average woman has in her lifetime if, at each year
of age, she experiences the average birthrate
occurring in the general population of similarly
aged women.
Toxic Release Inventory—A system for reporting
toxic emissions releases from individual facilities
in the United States. By making the data public, it
was designed to warn communities of the risks
they face and to encourage reductions prior to
regulation.
Toxicity—The degree of harm caused to living organ-
isms as a result of exposure to the substance.
Transactions Costs—Costs incurred in attempting
to complete transactions. (For example, in buying
a home, these might include payments to the
broker for arranging the sale, to the bank for one-
time special fees, and to the government for the
required forms. The value of the time expended in
negotiating would also be a transactions cost.)
Transfer Coefficient—A coefficient used in simulat-
ing pollutant flows. It relates the degree to which
pollution concentrations at a specific receptor site
are increased by a one-unit increase in emissions
from a specific source.
Transfer Cost—A cost to a private party that is not
a cost to society as a whole, because it involves a
transfer of net benefits from one component of
society to another.
Transferability—Property rights can be exchanged
among owners on a voluntary basis.
Troposphere—The atmosphere that is closest to the
earth. Its depth ranges from about 10 miles over
the equator to about five miles over the poles.
633Glossary
Two-Part Charge—As used in water management,
this type of charge combines volume pricing with
a monthly fee that doesn’t vary with the amount
used. The monthly fee is designed to help cover
fixed costs.
Underallocation—Less-than-optimal levels of a
resource are dedicated to a given use or time
period.
Uniform Emission Charge—A charge on effluent
that applies the same per-unit rate to all sources
regardless of their size or location.
Uniform Treatment—A strategy to reduce effluent
levels by a specified percentage at each emissions
level.
Uniformly Mixed Pollutants—For these pollu-
tants, the damage done to the environment
depends on the amount of emissions that enters
the atmosphere. The location of emissions is not
a matter of policy concern. (Examples include
ozone-depleting gases and greenhouse gases.)
User Cost—Opportunity cost created by scarcity.
It represents the value of an opportunity forgone
when the resource can no longer be used in
its next-best use. (For example, for a unit of a
depletable resource used now, the user cost is the
net benefits that would have been received by sav-
ing it and using it during the next time period.)
Usufruct Right—Holders of this right may use a
resource (normally subject to restrictions), but do
not have full ownership rights.
Variable Cost—Production costs that vary with
output.
Volume Pricing—Making the cost of the service a
function of the volume used. Used both in trash
disposal and water distribution.
Weak Form of the Global Scarcity Hypothesis—
According to this hypothesis, production is able
to keep pace with population growth, but the sup-
ply curve is sufficiently steeply sloped that food
prices increase faster than other prices in general;
the relative price of food increases over time, and
the problem is affordability rather than physical
availability.
Weak Sustainability—Resource use by previous
generations should not exceed a level that would
prevent future generations from achieving a level
of well-being at least as great. This definition of
sustainability is fulfilled if the total capital stock
(natural capital plus physical capital) does not
decline.
Welfare Measure—A measure of development that
increases or decreases in relation to how well-off
society is.
Wet Deposition—Occurs when air pollutants fall to
land or water during rain or snow events.