489 research outputs found
Information technology and productivity: where are we now and where are we going?
Productivity growth in the U.S. economy jumped during the second half of the 1990s, a resurgence that many analysts linked to developments in information technology (IT). However, shortly after this consensus emerged, demand for IT products fell sharply, leading to a debate about the connection between IT and productivity and about the sustainability of the faster growth. ; This article contributes to this debate in two ways. First, the authors provide updated estimates of the proximate sources of growth using a growth accounting framework that focuses on information technology. Their results confirm that the acceleration in labor productivity after 1995 was driven by the greater use of IT capital goods and the more rapid efficiency gains in the production of these goods. Second, to assess whether the pickup in productivity growth is sustainable, the authors analyze the steady-state properties of a multisector growth model. This exercise generates a range for labor productivity growth of 2 percent to 2 3/4 percent per year, which suggests that much-and possibly all-of the resurgence is sustainable. ; The analysis also highlights that future increases in output will depend on the pace of technological advance in the semiconductor industry and on the extent to which products embodying these advances diffuse through the economy.Information technology ; Productivity ; Technology ; Economic development
Les technologies de lâinformation et la productivitĂ©Â : situation actuelle et perspectives dâavenir
Dans la deuxiĂšme moitiĂ© des annĂ©es quatre-vingt-dix, la croissance de la productivitĂ© de lâĂ©conomie amĂ©ricaine a rebondi, un phĂ©nomĂšne que nombre dâanalystes ont attribuĂ© aux technologies de lâinformation. Cependant, peu de temps aprĂšs que ce consensus se soit imposĂ©, la demande pour les produits de technologies de lâinformation sâeffondrait, relançant un vif dĂ©bat sur le lien entre les technologies de lâinformation et la productivitĂ©, de mĂȘme que sur la durabilitĂ© Ă©ventuelle dâune croissance aussi forte. Nous apportons notre contribution Ă ce dĂ©bat de deux maniĂšres : premiĂšrement, dans le but dâĂ©valuer la robustesse de notre argumentation antĂ©rieure, nous prolongerons, jusquâĂ la fin de 2001, notre analyse de la comptabilitĂ© de la croissance, dont nous avons dĂ©jĂ publiĂ© les rĂ©sultats (Oliner et Sichel, 2000a). Les nouveaux rĂ©sultats confirment les conclusions de nos travaux antĂ©rieurs : la croissance accĂ©lĂ©rĂ©e de la productivitĂ© du travail aprĂšs 1995 dĂ©coule principalement de lâusage croissant des biens dâĂ©quipement de type technologies de lâinformation et de gains dâefficacitĂ© accrus du cĂŽtĂ© de leur productionâ; deuxiĂšmement, nous analyserons les propriĂ©tĂ©s de rĂ©gime dâĂ©tat stationnaire dâun modĂšle de croissance multisectoriel, afin de jauger la durabilitĂ© potentielle dâun tel regain de productivitĂ©. Nous en dĂ©duirons une fourchette de valeurs pour la croissance de la productivitĂ© du travail, se situant entre 2 % et 2 Ÿ % par annĂ©e, ce qui laisse prĂ©sager que lâessentiel â sinon la totalitĂ© â de ce regain de vitalitĂ© pourrait ĂȘtre durable.Productivity growth in the U.S. economy jumped during the second half of the 1990s, a resurgence that many analysts linked to information technology (IT). However, shortly after this consensus emerged, demand for IT products fell sharply, leading to a lively debate about the connection between IT and productivity and about the sustainability of the faster growth. We contribute to this debate in two ways. First, to assess the robustness of the earlier evidence, we extend the growth-accounting results in Oliner and Sichel (2000a) through 2001. The new results confirm the basic story in our earlier work â that the acceleration in labor productivity after 1995 was driven largely by the greater use of IT capital goods and by the more rapid efficiency gains in the production of IT goods. Second, to assess whether the pickup in productivity growth is sustainable, we analyze the steady-state properties of a multi-sector growth model. This exercise generates a range for labor productivity growth of 2 percent to 2 Ÿ percent per year, which suggests that much â and possibly all â of the resurgence is sustainable
How Fast Do Personal Computers Depreciate? Concepts and New Estimates
This paper provides new estimates of depreciation rates for personal computers using an extensive database of prices of used PCs. Our results show that PCs lose roughly half their remaining value, on average, with each additional year of use. We decompose that decline into age-related depreciation and a revaluation effect, where the latter effect is driven by the steep ongoing drop in the constant-quality prices of newly-introduced PCs. Our results are directly applicable for measuring the depreciation of PCs in the National Income and Product Accounts (NIPAs) and were incorporated into the December 2003 comprehensive NIPA revision. Regarding tax policy, our estimates suggest that the current tax depreciation schedule for PCs closely tracks the actual loss of value in a zero-inflation environment. However, because the tax code is not indexed for inflation, the tax allowances would be too small in present value for inflation rates above the very low level now prevailing.
Explaining a Productive Decade
This paper analyzes the sources of recent U.S. productivity growth using both aggregate and industry-level data. The paper confirms the central role of information technology in the productivity revival during 1995-2000 and shows that it played a significant, although smaller, role after 2000. Productivity growth after 2000 appears to have been boosted by industry restructuring and cost cutting in response to profit pressures, an unlikely source of future strength. In addition, the incorporation of intangible capital into the growth accounting framework somewhat diminishes estimates of labor productivity's performance since 2000 and makes the gain during 1995-2000 look larger than in the official data. Finally, the paper examines the outlook for trend growth in labor productivity; the resulting estimate, which is subject to much uncertainty, is centered at 2 1/4 percent a year, faster than the lackluster pace that prevailed before 1995 but somewhat slower than the 1995-2000 average.macroeconomics, productivity growth, labor productivity
Spreading lengths of Hermite polynomials
The Renyi, Shannon and Fisher spreading lengths of the classical or
hypergeometric orthogonal polynomials, which are quantifiers of their
distribution all over the orthogonality interval, are defined and investigated.
These information-theoretic measures of the associated Rakhmanov probability
density, which are direct measures of the polynomial spreading in the sense of
having the same units as the variable, share interesting properties: invariance
under translations and reflections, linear scaling and vanishing in the limit
that the variable tends towards a given definite value. The expressions of the
Renyi and Fisher lengths for the Hermite polynomials are computed in terms of
the polynomial degree. The combinatorial multivariable Bell polynomials, which
are shown to characterize the finite power of an arbitrary polynomial, play a
relevant role for the computation of these information-theoretic lengths.
Indeed these polynomials allow us to design an error-free computing approach
for the entropic moments (weighted L^q-norms) of Hermite polynomials and
subsequently for the Renyi and Tsallis entropies, as well as for the Renyi
spreading lengths. Sharp bounds for the Shannon length of these polynomials are
also given by means of an information-theoretic-based optimization procedure.
Moreover, it is computationally proved the existence of a linear correlation
between the Shannon length (as well as the second-order Renyi length) and the
standard deviation. Finally, the application to the most popular
quantum-mechanical prototype system, the harmonic oscillator, is discussed and
some relevant asymptotical open issues related to the entropic moments
mentioned previously are posed.Comment: 16 pages, 4 figures. Journal of Computational and Applied Mathematics
(2009), doi:10.1016/j.cam.2009.09.04
Quantifying the effects of hydrogen on carbon assimilation in a seafloor microbial community associated with ultramafic rocks
Thermodynamic models predict that H2 is energetically favorable for seafloor microbial life, but how H2 affects anabolic processes in seafloor-associated communities is poorly understood. Here, we used quantitative 13C DNA stable isotope probing (qSIP) to quantify the effect of H2 on carbon assimilation by microbial taxa synthesizing 13C-labeled DNA that are associated with partially serpentinized peridotite rocks from the equatorial Mid-Atlantic Ridge. The rock-hosted seafloor community was an order of magnitude more diverse compared to the seawater community directly above the rocks. With added H2, peridotite-associated taxa increased assimilation of 13C-bicarbonate and 13C-acetate into 16S rRNA genes of operational taxonomic units by 146% (±29%) and 55% (±34%), respectively, which correlated with enrichment of H2-oxidizing NiFe-hydrogenases encoded in peridotite-associated metagenomes. The effect of H2 on anabolism was phylogenetically organized, with taxa affiliated with Atribacteria, Nitrospira, and Thaumarchaeota exhibiting the most significant increases in 13C-substrate assimilation in the presence of H2. In SIP incubations with added H2, an order of magnitude higher number of peridotite rock-associated taxa assimilated 13C-bicarbonate, 13C-acetate, and 13C-formate compared to taxa that were not associated with peridotites. Collectively, these findings indicate that the unique geochemical nature of the peridotite-hosted ecosystem has selected for H2-metabolizing, rock-associated taxa that can increase anabolism under high H2 concentrations. Because ultramafic rocks are widespread in slow-, and ultraslow-spreading oceanic lithosphere, continental margins, and subduction zones where H2 is formed in copious amounts, the link between H2 and carbon assimilation demonstrated here may be widespread within these geological settings
International evidence on business cycle duration dependence
We provide an investigation of duration dependence in prewar business expansions, contractions, and whole cycles for France, Germany, and Great Britain. Our results, obtained using both nonparametric and parametric procedures, generally indicate the presence of positive duration dependence in expansions and whole cycles but not in contractions. Our results corroborate those of our earlier studies of the United States.Business cycles
Theoretical and experimental study of cylindrical shock and heterogeneous detonation waves
A simplified theory of blast initiation of detonations in clouds of fuel in gaseous or droplet form is developed and agrees with the experiments described below. The flow is at first dominated by the strong blast wave but transition from blast to detonation behavior occurs near a critical radius r* where the blast energy and the heat of combustion contained in r r* are equal. The complex flow in this transition region cannot be determined analytically. In the simplified theory the details of the transition region are ignored but the flow is represented by the self-similar solution for a strong blast wave for r r* and by the self-similar detonation solution for r > r*.The development of a sectored shock tube to study cylindrical shock waves and two-phase detonations is described. Data are presented for shock waves as well as for blast initiated detonations of a monodisperse spray of 400 [mu] kerosene droplets in air at standard conditions. Two regimes of propagation were established experimentally: (1) the subcritical energy regime, where decoupling of shock and reaction zone results in a strong blast wave type decay and, (2) the supercritical energy regime, where the initially overdriven cylindrical detonation decays, at some critical radius, to its Chapman-Jouguet state. Experimentally determined critical radii and steady-state detonation velocity agree very well with theoretical predictions. Detonation velocity was found to be constant at the plane C-J value for radius greater than the critical radius.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22402/1/0000852.pd
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