ANALISIS UNIVARIANTE:
ANALISIS MULTIVARIANTE:
I. C 95 % EXP(B) Inf Sup.
6.2. OBJETIVOS SECUNDARIOS :
6.2.2. EVALUACIÓN DE LAS COMPLICACIONES P.O :
Economic growth in ADAGE comes from four sources: growth in the available labor supply from population growth and changes in labor productivity, capital accumulation through savings and investment, increases in stocks of natural resources, and technological change associated with improvements in manufacturing and energy efficiency. This section
discusses these dynamic processes (data underlying actual growth paths in the model are discussed in Sections 4 and 5).
Materials
σmat = 0 σva = 1.0Crude Oil
Output
Value-Added
Composite
Capital
Labor
3.1 Labor Growth
At the beginning of the model horizon, households in each region in ADAGE are endowed with an initial supply of labor, the value of which is shown in the economic accounts used by the model. Similar to other CGE models, ADAGE then relies on exogenously specified rates of growth to determine how the value of labor endowments increases over time. Using the assumption of Harrod-neutral technical progress, the model tracks increases in effective units of labor available across the economy, encompassing both population growth and improvements in labor productivity. This approach facilitates incorporation of economic- growth forecasts from IEA and EIA, which also provide other forecasts used in ADAGE.
3.2 Investment, Capital Stocks, and Adjustment Dynamics
Decisions regarding savings by households and the associated capital formation control many of the behavioral responses estimated for policies. ADAGE models these decisions using a forward-looking, full intertemporal optimization approach in which households have perfect foresight and maximize the present value of all future consumption.26 By allowing
agents to anticipate new policies, ADAGE can show how people will begin to prepare for policies that are announced today, but that may not begin until sometime in the future. The savings motivated through these expectations about future needs for capital determine aggregate capital stocks in ADAGE. Both the GTAP and IMPLAN datasets provide details on the types of goods and services used to produce the investment goods underlying each economy’s initial capital stocks. The model uses these data to specify an aggregate investment sector generating the capital needed by the economy. The data sources, however, do not contain a representation of actual capital stocks, so it is necessary to calibrate these stocks from the observed earnings generated by the unobserved capital stocks.27 Typically, capital stock data, even if available, are not considered as reliable as
capital earnings data, so this calibration approach may be used even if stock data are available.28
Dynamic processes controlling how capital stocks evolve over time will determine the transition path the economy takes from its initial baseline forecast to a new equilibrium in response to policies. ADAGE models these dynamics through quadratic adjustment costs
26The theoretical basis for this approach comes from Ramsey (1928), Cass (1965), and Koopmans (1965).
27Capital earnings (Ke) are equal to the interest rate (r) plus the depreciation rate (δ) times the capital stock. This allows the initial stock of capital (Ks) to be calculated as Ks = Ke / (r+ δ). The
interest rate in ADAGE is assumed to equal 5 percent, based on the MIT EPPA model, and the overall depreciation rate is set at 7 percent, based on a weighted average rate across the capital assets shown in Table 4-7.
associated with installing new capital (Uzawa, 1969).29 These installation costs depend on
the rate of gross investment in relation to the existing stock of capital and are expressed as
+
=
t t t tK
J
J
I
2
1
φ
where Itis gross investment (in period t), Jt is net investment, Kt is the existing capital
stock, and
φ
reflects the speed of adjustment.30 The formulation implies that rapidchanges in capital stocks are expensive and that the rate of adjustment will decline as adjustment costs increase.
Available capital stocks in time period t (Kt) are equal to new net investment plus
depreciated capital left from the previous time period:
t t
t
K
J
K
+1=
(1−δ)+
.Thus, net investment has to be sufficient to cover both economic growth (generating new capital demands) and depreciation of existing capital. Capital stocks are assumed to be perfectly malleable across industries within each region in ADAGE.
3.3 Fossil-Fuel Resources
Fossil-fuel resources (coal, crude oil, and natural gas), which are endowed to households in ADAGE, evolve over time through changes in quantities and prices. Expected future
quantities and prices are matched to WEO and AEO forecasts from IEA and EIA (see Section 5); however, these forecasts do not provide information on the amount of resources
available for extraction or the costs associated with extracting them. To address these limitations, ADAGE generates resource supply elasticities around forecasted production paths of the resources.
The supply elasticities reflect how production costs rise as more resources are extracted, along with effects of depleting the fossil-fuel resources. By selecting an elasticity of substitution between a resource and other production inputs in these industries (elasticity
σgr in Figure 2-7), a given resource supply elasticity can be calibrated.31 Fossil-fuel price
paths from WEO and AEO forecasts are also matched by adjusting growth rates for the
29See Lau, Pahlke, and Rutherford (2002) for discussion of this and other modeling techniques related to dynamics.
30The adjustment cost parameter, φ, is set at 0.2, following Bovenberg and Goulder (2000).
31ADAGE uses an approach to resource supply elasticities that is similar to the EPPA model. Algebraic calculations (Babiker et al., 2001) can demonstrate that the resource supply elasticity (ηs) is equal to the substitution elasticity (σgr), adjusted by the share of inputs of natural resources used to produce output from the resource industry (Snr): ηs= σgr* (1- Snr) / Snr.
fixed-factor inputs to resource production so that prices in the baseline ADAGE solution are calibrated, as closely as is feasible, to desired forecasts.32
3.4 Energy Consumption
Energy consumption per unit of output tends to decrease over time through improvements in production technologies and energy conservation (although it is not necessarily true in developing countries as they move into more energy-intensive and less labor-intensive manufacturing processes). The energy mix in an industry may also shift as production techniques change. For example, natural gas use in electricity generation in the United States rose by almost 60 percent between 1990 and 2000, while coal use rose by less than 25 percent (EIA, Annual Energy Review 2003). When examining environmental policies, it is essential to include these technology shifts in the baseline forecasts of ADAGE.
Similar to other CGE models, ADAGE captures these energy consumption changes through autonomous energy-efficiency improvement (AEEI) parameters. An AEEI index is specified in the model for each fuel type and each industry. These indices alter the physical amount of energy needed to produce a given quantity of output by accounting for improvements in energy efficiency, conservation, and switching among fuel types.33 Rather than apply
generic trends to these parameters based on overall energy-efficiency improvements from historical data, AEEIs are used in ADAGE to match expected trends in energy consumption from WEO and AEO forecasts.