درسهایی از تجدید حیات رشد اقتصادی ایالات متحده

Table 1 reports our estimates of the sources of economic growth from Eq. (2). For the period 1959–2001, output grew 3.38% per year. Capital input contributed 1.62 percentage points per year and labor input followed in importance with 1.16 percentage point per year. The remaining 0.59 percentage points reflect growth in TFP. These results are consistent with the other recent growth accounting estimates, including CEA (2001), Jorgenson and Stiroh (2000), Jorgenson (2001), Jorgenson et al. (2002b), and Oliner and Sichel (2000, 2002). Our data also reveal substantial acceleration in output growth after 1995. The growth rate of output increased from 2.78% per year for 1973–1995 to 4.07% for 1995–2000, reflecting a substantial acceleration in IT investment and a modest deceleration in non-IT investment. For 1995–2001, which includes the US recession that began in March 2001, output growth was 3.55% per year. This is considerably slower, and we focus our attention on the period 1995–2000 to avoid the cyclical effects of the 2001 recession. On the input side, more rapid capital accumulation contributed 0.68 percentage points to the post-1995 acceleration through 2000, while faster growth of labor input contributed 0.25 percentage points and accelerated TFP growth the remaining 0.36 percentage points. These estimates are smaller when 2001 is included. Finally, the contribution of capital input from IT increased from 0.42 percentage points per year for 1973–1995 to 0.98 for 1995–2000, an increase of 0.56 percentage points, while the contribution of other capital increased by only 0.12 percentage points. The last panel in Table 1 presents an alternative decomposition of the contribution of capital and labor inputs, using Eqs. (5) and (6). The contributions of capital and labor inputs reflect the contributions of capital quality and capital stock, as well as labor quality and hours worked:

The unusual combination of more rapid growth and lower inflation in the United States from 1995 to 2000 touched off a strenuous debate among economists about whether improvements in US economic performance could be sustained. Despite the recent slowdown in the economy in general and in information technology (IT) in particular, this debate has given way to a broad consensus that IT is the key to understanding the American growth resurgence and recent research has turned to the future of productivity growth. In this paper we review the most recent evidence on growth in the United States and present a model for projecting future productivity growth. Our primary conclusion is that, despite downward revisions to the gross domestic product (GDP) and investment in the annual revisions of the US National Income and Product Accounts (NIPA) in July of 2001 and 2002, the US productivity revival remains intact with IT as the predominant source. The story begins with an increase in total factor productivity (TFP) growth in the IT-producing sectors (computer hardware, software, and telecommunications), which led to falling relative prices and induced capital deepening in IT equipment. These two contributions account for a majority of the acceleration in labor productivity growth after 1995.

Our primary conclusion is that a consensus has emerged about trend rates of growth for output and labor productivity. While productivity is projected below the pace seen in late 1990s, we conclude the US productivity revival is likely to remain intact for the intermediate future and there is no indication of a return to the slow growth period of the 1970s and 1980s. Our second conclusion, however, is that trend growth rates are subject to considerable uncertainty. For the US economy this can be identified with the future product cycle for semiconductors and its impact on the production of other high-tech gear. The switch from a three-year to a two-year product cycle in 1995 produced a dramatic increase in the rate of decline of IT prices. This is reflected in the investment boom of 1995–2000 and the massive substitution of IT capital for other types of capital that took place in response to price changes. The issue that must be confronted by policy-makers is whether this two-year product cycle can continue, and whether firms will continue to respond to the dramatic improvements in the performance/price ratio of IT investment goods. These are the fundamental uncertainties surrounding our productivity projections.