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In recent years, measured TFP growth in the US has declined. We argue that two forces contributed to this decline: the mismeasurement of intangible capital, and rising markups. Markups affect input shares, while intangibles omitted from measures of investment affect measured capital growth, each potentially generating downward bias in measured TFP growth. Most importantly, when both forces are simultaneously present, their effects reinforce each other and amplify the downward bias in measured TFP growth. Using input-output data, we estimate that this mechanism could account for one-third to two-thirds of the decline in measured TFP growth.

Increasing investment is often recommended as a prescription for increasing productivity, stoking demand, and addressing other causes of low growth or prospective crises in the U.S. economy. Yet an examination of investment suggests that it is not poised to fill this role. Private sector investment has undergone a slow transformation, shifting from structures and equipment investment, with the latter enjoying a long trend of falling prices, to a rising role for intellectual property, software, and other intangible capital. The high depreciation rate associated with this new capital imposes a drag on net investment and hence on capital accumulation. Public investment remains mostly focused on infrastructure but has fallen in half as a share of GDP since its peak in the 1950s. These trends emphasize the potential importance of new types of private capital and their implications for growth, as well as the declining role of public investment, including federal R&D.

Investment in intangible capital such as R&D has increased dramatically since the 1990s. However, productivity growth remains sluggish in recent years. One potential reason is that a significant share of the increase in intangible investment is geared toward consumer products such as pharmaceutical drugs with limited spillovers to productivity. We document that a significant share of R&D spending in the United States is done by pharmaceutical firms and geared to developing drugs for older patients. Increased life expectancy and quality of life for the elderly increases welfare but may not be reflected in estimates of total factor productivity.

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.

When investment decisions cannot be reversed and returns to capital are uncertain, the firm faces a higher user cost of capital than if it could reverse its decisions. This higher user cost tends to reduce the firm's capital stock. Opposing this effect is the irreversibility constraint itself: when the constraint binds, the firm would like to sell capital but cannot. This effect tends to increase the firm's capital stock. We show that a firm with irreversible investment may have a higher or a lower expected capital stock, even in the long run, compared to an otherwise identical firm with reversible investment. Furthermore, an increase in uncertainty can either increase or decrease the expected long-run capital stock under irreversibility relative to that under reversibility. However, changes in the expected growth rate of demand, the interest rate, the capital share in output, and the price elasticity of demand all have unambiguous effects.

We characterize a firm's optimal factor adjustment when any number of factors face “kinked” linear adjustment costs so that all factor accumulation is costly to reverse. We first consider a general non-stationary case with a concave operating profit function, unrestricted form of uncertainty and a horizon of arbitrary length. We show that the optimal investment strategy follows a control limit policy at each point in time. The state space of the firm's problem is partitioned into various domains, including a continuation region where no adjustment should optimally be made to factor levels. We then consider two specific model classes and exploit their special structure to derive expressions for their continuation regions.Journal of Economic LiteratureClassification Numbers: D92, E22, E24.

This paper derives closed-form solutions for the investment and value of a competitive firm with a constant-returns-to-scale production function and convex costs of adjustment. Solutions are derived for the case of irreversible investment as well as for reversible investment. Optimal investment is a non-decreasing function of q, the shadow value of capital. Relative to the case of reversible investment, the

While there has been a substantial increase in the return to college (the college premium), college attainment has stagnated. We show that these facts can be reconciled by allowing for uncertainty in college payoffs, in particular around college completion and earnings, with borrowing. With plausible measures of risk and credit availability, even modestly prepared potential enrollees are already inframarginal. Being less-well prepared and poorer, they face a lower expected payoff and more risk. Those more responsive to the college premium already enroll in, and complete, college.

We develop a two sector general equilibrium model with capital accumulation and convex adjustment costs. We use the model to study capital asset pricing and reallocation, as well as optimal consumption and investment decisions. With two sectors, the consumer balances diversification against the potential productivity and efficiency gains of investing more heavily in one sector. The general framework nests and ex-tends standard equilibrium macro-asset pricing models. We show conditions under which aggregates are immune to the distribution of capital and in contrast, when the distribution becomes crucial for both sectoral and aggregate values. Applications of the framework highlight the importance of heterogeneity and capital liquidity - the ability to reallocate capital - for economic growth and asset pricing. Misallocated capital creates risk and reduces utility, but correcting it through capital reallocation reduces efficiency and growth.