recessions, a world war, and other 
major shocks to the U.S. economy. In 
each case, the national economy has 
recovered, and it is expected to 
continue to do so in the future. The 
basic forces for longrun economic 
growth will continue. Wharton 
Econometrics projections indicate that 
the gross national product will reach 
$15.6 trillion in 2040, over four times 
its level in 1986. Associated disposable 
personal income rises to $9.6 trillion, 
over a threefold increase. Per capita 
disposable income will increase over 
2.5 times, to $28,790. 
The assumptions about population, 
gross national product, and disposable 
personal income suggest a future with 
many more people with greater 
purchasing power—a future with 
strong growth in demand continuing 
the historical trend. 
Technological and 
Institutional Change 
Past changes in demands and supplies 
have reflected the interactions and 
direct influences of institutional and 
technological changes. We assume that 
the stream of institutional and 
technological changes will continue 
and that the effects of these changes on 
demands and supplies of renewable 
resources will be similar to those that 
have taken place and are included in 
the historical data base used in making 
the projections. For some products and/ 
or processes, however, we identified 
possible future technological changes 
and made specific allowances for them 
in projections (fig. 3). 
Institutional changes that lead to the 
reservation of forests and rangelands 
for designated uses such as wilderness, 
parks, and wildlife refuges have 
occurred for a long time. This 
development is specifically taken into 
Figure 3—Allowances have been made for 
expected future changes in technology. 
account in the projections of forest and 
rangeland areas. Assumptions on 
important technological changes 
affecting product yields and other uses 
of the renewable resources are 
specified in the individual resource 
Assessment documents as appropriate. 
Energy Costs 
The apparent consensus view of the 
long-term outlook for energy costs can 
be confusing because of the weakness 
of energy prices in the 1980's. 
Projections of the U.S. Department of 
Energy reflect the consensus view of 
the long-term outlook. These 
projections show world crude oil prices 
increasing from $12.22 per barrel in 
1986 to $50 per barrel in 2020. Prices 
are in 1982 dollars net of inflation or 
deflation. The price of $50 is assumed 
to be high enough to stimulate 
development of alternative energy 
sources with implications for the 
demand for timber and timber 
products, especially fuelwood. Thus 
energy prices are assumed constant 
from 2020 through 2040. Rising energy 
prices have been taken into account in 
projecting demands and supplies for 
those products. 
Capital Availability and 
Investments 
Capital availability has occasionally 
been raised as an issue in making 
judgments about the likelihood that 
future output levels will be realized. 
Over the years, various analyses have 
supported the assumption that capital 
would not be a limiting factor for 
future production levels. Wharton 
Econometrics projections of growth in 
gross national product indicate a 
growing economy with capital 
generation. Therefore, we assume that 
capital will not be a limiting factor for 
projected outputs of products from 
forest and range lands and associated 
waters. 
Future supplies will be determined in 
large measure by management intensity 
(the level of investment in forest and 
range lands and associated water 
resources). Assumptions about future 
management intensities vary by 
resource and are discussed as part of 
the supply outlook for each resource. In 
general, however, demand and supply 
projections are strongly influenced by 
the past historical trend of their basic 
determinants and reflect the effects of 
past public programs for assistance. 
