Using a normalized CES function with factor-augmenting technical progress, we estimate a supply-side system of the U.S. economy from 1953 to 1998. Avoiding potential estimation biases that may have occurred in earlier studies and putting a high emphasis on data consistency, we obtain robust results not only for the aggregate elasticity of substitution but also for the parameters of labor and capital augmenting technical change. We find that the elasticity of substitution is significantly below unity and that technical progress shows an asymmetrical pattern where the growth of labor-augmenting technical progress is exponential, while that of capital is hyperbolic or logarithmic. Copyright by the President and Fellows of Harvard College and the Massachusetts Institute of Technology.

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4Non-technical summary 5

The elasticity of substitution between capital and labor and, in turn, the direction of technical change are critical parameters in many fields of economics. Until recently, though, the application of production functions with specifically non‐unitary substitution elasticities (i.e., non‐Cobb–Douglas) was hampered by empirical and theoretical uncertainties. As recently revealed, ‘normalization’ of production‐technology systems holds out the promise of resolving many of those uncertainties. We survey and assess the intrinsic links between production (as conceptualized in a production function), factor substitution (as made most explicit in Constant Elasticity of Substitution functions) and normalization (defined by the fixing of baseline values for relevant variables). First, we recall how the normalized Constant Elasticity of Substitution function came into existence and what normalization implies for its formal properties. Then we deal with the key role of normalization in recent advances in the theory of business cycles and of economic growth. Next, we discuss the benefits normalization brings for empirical estimation and empirical growth research. Finally, we identify promising areas of future research.

The objectives of this paper are : first, to quantify the stabilization welfare gains from commitment; second, to examine how commitment to an optimal rule can be sustained as an equilibrium and third, to find a simple interest rate rule that closely approximates the optimal commitment one. We utilize an influential empirical micro-founded DSGE model, the euro area model of Smets and Wouters (2003), and a quadratic approximation of the representative household's utility as the welfare criterion. Importantly, we impose the effect of a nominal interest rate zero lower bound. In contrast with previous studies, we find significant stabilization gains from commitment: our central estimate is a 0.4 − 0.5% equivalent permanent increase in consumption, but in a variant with a higher degree of price stickiness, gains of over 2% are found. We also find that a simple optimized commitment rule with the nominal interest rate responding to current inflation and the real wage closely mimics the optimal rule. JEL Classification: E52, E37, E58Keywords: Monetary rules, commitment, discretion, welfare gains. ECB Working Paper Series No 709 January 2007 Non-technical SummaryThis paper has three principle objectives. First, to quantify the stabilization gains from commitment in terms of household welfare. Second, to examine how commitment to an optimal or approximately optimal rule can be sustained as an equilibrium in which reneging hardly ever occurs. And finally, to find a simple interest rate rule that closely approximates the optimal commitment (and complex) rule.We utilize an influential empirical micro-founded dynamic stochastic general equilibrium (DSGE) model of the euro area in which there are four sources of time-inconsistency: from forward-looking pricing, consumption, investment and wage setting. In the absence of commitment, following a shock which diverts the economy from its steady state and given expectations of inflation, the opportunist policy-maker can increase or decrease output by reducing or increasing the interest rate which increases or decreases inflation. This results in a higher variability of inflation and the nominal interest rate under discretion. The latter means that the interest rate zero lower bound constraint is tighter under discretion and its presence increases the stabilization gains from commitment. The constraint can be relaxed by increasing the steady state inflation rate, but at a cost of an increase in the deterministic component of the welfare loss.In terms of methodology our welfare-based loss function uses the 'small distortions' quadratic approximation to the consumer's utility which is accurate if the steady state is close to the social optimum. In assessing this condition we highlight a neglected aspect of typical New Keynesian models: external habit in consumption tends to make labour supply and the natural rate of output too high compared with the social optimum. If the habit effect is sufficiently high and labour market and product market distortions are not too big then, ...