GILBERTO VELEZ VENTURA APODERADO LEGAL

To simplify, assume that the labor force is constant. Now, suppose that a growth accountant failed to incorporate investment-specific technological progress into his analysis. He would construct his capital stock series according to

dk/dt = ie _{− δ}k.e (36) This corresponds to measuring the stock of capital at historical cost in output units. Using (2) he would obtain the following series describing neutral technological progress

Since by assumption all growth in output must derive from growth in the capital stock, it must transpire from (3) that gy = αgk so that

g_ez = α³gk− g_ek

´

.

Hence, any change in the measured Solow residual arises solely from mismeasurement in the capital stock. To gain an understanding of this equation, suppose that the economy was gliding along a balanced growth path. From (4) and (36) it is clear that in this situation

gk− g_ek = gq,

implying

g_ez = αgq.

While the growth accountant may have killed off investment-specific technological progress in his misspecification of the law of motion of capital it has resurrected itself in the form of neutral technological progress.

The model demands that GDP should be measured in consumption units, the numeraire. Doing so is important What would happen if the growth accountant used standard real GDP numbers. Specifically, let GDP be measured as

e

y = c + pqi,

where p is some base year price for capital goods. Applying (2) the growth accountant would obtain

= g_{ey− g}y. (37)

The difference in the growth rates between the traditional measure of GDP, y, ande

the consumption based one, y, will be picked up as neutral technological progress. Now,

g_ey = (c/y)ge c+ p(iq/y)ge i+ p(iq/y)ge q.

Along a balanced-growth path gc = gi = gy. Since q is growing, it must therefore

transpire that c/ye_{→ 0 and piq/}ye_{→ 1. Hence, asymptotically}

g_ey = gi+ gq = gy+ gq,

so that from (37)

g_ez = gq.

Once again, investment-specific technological progress has masqueraded itself as neu- tral technological progress.

9

Endnotes

& Jeremy Greenwood is a professor of economics at the University of Rochester. Boyan Jovanovic is a professor of economics at New York University and a research associate at the National Bureau of Economic Research. The authors thank Levent Kockesen for help with the research. The National Science Foundation and the C.V. Starr Center for Applied Economics at New York University are also thanked for financial support.

1. The average cost of implementation may, however, be declining in the number of users because of synergies in adoption.

2. Jovanovic and Rob (1998) compare Solow’s 1956 and 1960 frameworks against the backdrop of cross country growth-experience.

3. “We should like to have both a rapid increase in aggregate output and stability in its composition — the former to keep pace with expanding wants, and the latter to avoid the losses of specialized equipment of entrepreneurs and crafts of employees and creating ‘sick’ industries in which resources are less mobile than customers. It is highly probable that the goals are inconsistent.” (Stigler 1947, p. 30)

4. In fact over the whole period it grew on average at the paltry rate of 0.96 percent per year.

5. Benhabib and Rustichini (1991) relax this assumption and allow for a variable rate of substitution in production between capital stocks of different vintages.

6. This structure has been used Greenwood, Hercowitz and Krusell (1997) for growth accounting. Hulten (1992) employs a similar setup, but replaces the resource constraint with c + ieq + is = y. See Greenwood, Hercowitz and Krusell (1997) for a

discussion on the implications of this substitution.

7. This is what Greenwood, Hercowitz and Krusell (1997) estimated.

8. The second part of the Appendix works out what would happen if a growth accountant failed to incorporate investment-specific technological advance into his analysis.

9. It makes sense that under constant returns to scale only the aggregate amount of investment matters, and not how it is divided among plants.

10. Even without these assumptions, the model will behave similarly in balanced growth. Assume for the moment that the number of plants is constant through time so that nτ = n and that zτ grows at rate gz. The supply of labor will be constant in

balanced growth. Now, along a balanced growth path output and investment must grow at a constant rate, gy. This implies that i = nk0/q must grow at this rate too.

Therefore, k0 must grow at rate gy + gq. Clearly, to have balanced growth all of the

kτ’s should grow at the same rate. Consequently, kτ will grow at rate gy + gq. It is

easy to deduce from (13) that the rate of growth in output will be given by gy = 1 y dy dt = 1 1_{− α}gz+ α 1_{− α}gq.

This formula is identical in form to (9). [To see this set αs = 0 and αe= α in (9)].

11. From the previous footnote, it is known that along a balanced growth path k0(t) must grow at rate gy+ gq, where gy is the growth rate of output, and gq is the

growth rate of 1/q. It is easy to check that gy + gq = gq/(1− α) ≡ κ.

12. For instance, David (1991) attributes the slow adoption of electricity in manu- facturing during the early 1900s partly to the durability of old plants using mechanical power derived from water and steam. Those industries undergoing rapid expansion and hence rapid net investment – tobacco, fabricated metal, transportation and equipment – tended to adopt electricity first.

(Federal Reserve Bank of Dallas 1997, Exhibit D). Search-theoretic models of tech- nological advance naturally attribute this trend to the secular improvement in the speed and quality of communication.

14. Unskilled labor’s share of income remains constant while skilled labor’s share increases.

15. They estimate that ln[(1 − θ)/θ] has grown at a rate of 3.6% since the 1970s. This yields roughly the right magnitude of the increase in the college/high school wage gap.

16. In order to simplify things, Arrow’s (1962) assumption that there are fixed, vintage-specific proportions between machines and workers in production is dropped. This assumption can lead to capital getting scrapped before the end of its physical life span. (In his analysis capital goods face sudden death at the end of their physical life span, unless they are scrapped first, as opposed to the gradual depreciation assumed here.) Also, Arrow assumes that machine producers’ efficiency is an isoelastic function of the cumulative number of machines produced, whereas here it’s assumed to be an isoelastic function of cumulative number of efficiency units produced.

17. It follows immediately that gk is increasing in ν, and decreasing in ρ.

18. The functional form of the learning curve is taken from Parente (1994). Zeckhauser (1968) considers a wider class of learning curves.

19. One caveat on Parente’s model: The choice of A0 _{is constrained by the fact}

could be removed by choosing a different form for the loss of expertise caused by upgrading. An example of a functional form that would accomplish this is

z0 = Ã A0 A !ϑ (zT − κ),

where zT is the level of expertise just before the adoption and ϑ < 0.

20. Chari and Hopenhayn (1991), and Jovanovic and Nyarko (1996) also focus on human-capital-based absorption costs. These models provide a microfoundation for why switching costs should be larger when the new technology is more advanced. This implies that when a firm does switch to a new technology, it may well opt for a technology that is inside the frontier. This implication separates the human capital vintage models from their physical capital counterparts, because the latter all imply that all new investment is in frontier methods.

Search frictions can also lead firms to adopt methods inside the technological frontier. In the models of Jovanovic and Rob (1989) and Jovanovic and MacDonald (1994) it generally doesn’t pay for firms to invest time and resources to locate the best technology to imitate.

21. Suppose that tastes are described by (21). Then, along a balanced-growth path r = ρ + gy = ρ + αgk. Hence, r − αgk = ρ.

22. This type of model may have some interesting transitional dynamics. Imagine starting off with some distribution of technologies where producers are bunched up around some particular technique. What economic forces will come to bear to en- courage them not to all upgrade around the same date in the future? How long will

it take for the distribution to smooth out?

23. Stimulating growth does not necessarily improve welfare. The sacrifice in terms of current consumption may be prohibitively high.

1940 1950 1960 1970 1980 1990 2000 Year 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 z

Fig. 1: Standard measure of neutral technological progress

1940 1950 1960 1970 1980 1990 2000 Year 1 2 3 4 5 6 p 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 q p q

Fig. 2: Relative price of equipment, p, and investment-specific technological progress, q

0 10 20 30 40 Years 0.7 0.8 0.9 1.0 1.1 1.2 Labor P roduc ti v it y -- lo gged Productivity Old Trend

Fig. 3: Transitional dynamics

0 10 20 30 40 Years 0.7 0.8 0.9 1.0 1.1 1.2 1.3 Labor P roduc ti v it y -- lo gged Benchmark Old Trend No Learning

0 2 4 6 8 10 12 14 16 18 20 Years 0.74 0.76 0.78 0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94 Labor P roduc ti v it y -- lo gged Immediate Diffusion Old Trend Benchmark

Fig. 5: Transitional dynamics – immediate diffusion

Time T o tal F a c tor P roduc tiv ity , A z Switching date Old New Lost Productivity