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The best predictor of current investment at the firm level is lagged investment. This lagged-investment effect is empirically more important than the cash-flow and Q effects combined. We show that the specification of investment adjustment costs proposed by Christiano et al. (2005) predicts the presence of a lagged-investment effect and that a generalized version of their model is consistent with the behavior of firm-level data from Compustat.

We derive a closed-form solution for Tobin's Q in a stochastic dynamic framework. We show analytically that investment is positively related to Tobin's Q and cash flow, even in the absence of adjustment costs or financing frictions. Both Q and investment move in the same direction as expected revenue growth, so changes in expected revenue growth induce Q and investment to comove positively. Similarly, shocks to current cash flow, arising from shocks to the user cost of capital in our model, cause investment and cash flow per unit of capital to comove positively. Furthermore, we show that this alternative mechanism for the relationship among investment, Q, and cash flow delivers larger cash flow effects for smaller- and faster-growing firms, as observed in the data. Moreover, the empirically small sensitivity of investment to Tobin's Q does not imply implausibly large adjustment costs in our model (since there are no adjustment costs). Calibrating the model generates values of Q similar to those in the data; investment is more sensitive to cash flow than it is to Q, and both responses are of empirically plausible magnitudes. Copyright 2011, Oxford University Press.

Heterogeneity is ubiquitous in firm-level and sectoral data. Equilibrium models, how-ever, typically assume a representative firm, as in Andrew B. Abel and Olivier J. Blanchard (1983). The representative firm paradigm leaves no role for the distribution of capital. We model capital reallocation in a general equilibrium model with two sectors. Capital adjustment costs capture illiquidity in our model, similar to Hirofumi Uzawa’s (1969) capital installation technology. We follow Fumio Hayashi (1982) in assuming that the production technology is linearly homogeneous, which allows us to focus on the sectoral distribution of capital, separately from the level of total capital. The two sectors may have different levels of productivity, and we show that the distribution of capital between the two sectors is the single state variable gov-erning investment, growth, and valuation in the economy.We analytically characterize prices and quan-tities, including investment, growth, the interest rate, and the price of capital (Tobin’s

This paper tests an optimal (S, s) rule in household durable purchases and examines directly the resulting aggregate expenditure dynamics. The observed decision rule responds to income uncertainty and growth as predicted by an (S, s) model resulting from transactions costs. Tests against liquidity constraints find that about half the households purchase according to an optimal (S, s) rule. Aggregating the (S, s) rule over households produces a cross-section distribution of durables holdings. The empirical distribution is similar to that predicted theoretically, as is its response to aggregate shocks. Furthermore, simulations of aggregate expenditure based on the household distribution exhibit dynamics consistent with those observed in the 1980s. Copyright 1994 by University of Chicago Press.

Do investment models …t …rm-level data? - which model …ts best? To answer this question we estimate alternative models using Compustat data. We …nd that both a version of the Hayashi (1982) and a model with decreasing returns to scale in production …t …rm-level data very well. Our estimates suggest that there is substantial measurement error in Q. This measurement error implies that the investment-cash-‡ow regressions that +� � =

When factors of production can be adjusted costlessly, the mix of factors can be considered separately from their scale. We examine factor choice and utilization when investment is irreversible and subject to a fixed cost, so that the capital stock is a quasi-fixed factor that is adjusted infrequently and by discrete amounts. We derive and analyze analytic approximations for optimal investment behavior, and show how the quasi-fixity of capital eliminates the dichotomy between factor mix and scale. We show that the quasi-fixity of capital can give rise to labor hoarding, even when labor is a purely flexible factor.

We develop a model in which the opportunity for a firm to upgrade its technology to the frontier (at a cost) leads to growth options in the firm's value; that is, a firm's value is the sum of value generated by its current technology plus the value of the option to upgrade. Variation in the technological frontier leads to variation in firm value that is unrelated to current cash flow and investment, though variation in firm value anticipates future upgrades and investment. We simulate this model and show that, consistent with the empirical literature, in situations in which growth options are important, regressions of investment on Tobin's Q and cash flow yield small positive coefficients on Q and larger coefficients on cash flow. We also show that growth options increase the volatility of firm value relative to the volatility of cash flow.

This paper extends the theory of investment under uncertainty to incorporate fixed costs of investment, a wedge between the purchase price and sale price of capital, and potential irreversibility of investment. In this extended framework, investment is a non-decreasing function of q, the shadow price of installed capital. There are potentially three investment regimes, which depend on the value of q relative to two critical values. For values of q above the upper critical value, investment is positive and is an increasing function of q, as is standard in the theory branch of the adjustment cost literature. For intermediate values of q, between two critical values, investment is zero. Although this regime features prominently in the irreversibility literature, it is largely ignored in the adjustment cost literature. Finally, if q is below the lower critical value, gross investment is negative, a possibility that is ruled out by assumption in the irreversibility of literature. In general, however, the shadow price q is not directly observable, so we present two examples relating q to observable varieties.