Notebook per
IdeaPF
Citation (APA): riccardo-mariani@libero.it. (2016). IdeaPF [Kindle Android version]. Retrieved from Amazon.com
Parte introduttiva
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Are Ideas Getting Harder to Find? Nicholas Bloom
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1. Introduction
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T
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Economic growth arises from people creating ideas, and the long-run growth rate is the product of two terms: the effective number of researchers and the research productivity of these people
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X CRESCITA E IDEE
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research effort is rising substantially, while research productivity is declining sharply.
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X EVIDENZA EMPIRICA DERL FENOMENO
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Moore’s Law,
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the empirical regularity that the number of transistors packed onto a computer chip doubles approximately every two years.
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x LEGGE DI MOORE
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a rate that has been remarkably steady for nearly half a century.
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c
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this growth has been achieved by putting an evergrowing number of researchers to work on pushing Moore’s Law forward. In particular, the number of researchers required to achieve the doubling of chip density today is more than 25 times larger than the number required in the early 1970s.
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x SEMPRE PIÙ RICERCATORI
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our case studies include agricultural productivity (corn, soybeans, cotton, and wheat) and medical innovations.
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x ALTRI DUE SETTORI
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Idea TFP for seed yields declines at about 5% per year. We find a similar rate of decline when studying the mortality improvements associated with all cancers and with breast cancer.
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X CANCRO
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Finally, we examine firm-level data from Compustat
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STUDIO STATISTICO
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idea TFP is declining in more than 85% of the firms in our sample. Averaging across firms, idea TFP declines at a rate of 12% per year.
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X ESIYO
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While existing varieties run into diminishing returns, perhaps new varieties are always being invented to stave this off.
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X POSSIBILITÀ DI COMPENSAZIONI
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To examine this case, we consider idea TFP for the economy as a whole. We once again find that it is declining sharply: aggregate growth rates are relatively stable over time, while the number of researchers has risen enormously.
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X TENDENZA CONFERMATA NELL EVONOMIA GLOBALE
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We find that idea TFP for the aggregate U.S. economy has declined by a factor of 48 since the 1930s, an average decrease of more than 5% per year.
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x FACTOR 48
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How is this possible?
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T
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declines in idea TFP must be offset by increased research effort,
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2. Idea TFP and Aggregate Evidence
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t
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2.1. The Conceptual Framework
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t
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2.2. Aggregate Evidence
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t
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consistent evidence
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idea TFP is declining at a substantial rate in virtually every place we look.
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x EVIDENZA
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This finding raises a natural question, however, which no doubt has occurred to you already: what if there is sharply declining idea TFP within each product line, but the main way that growth proceeds is by developing ever-better new product lines? First there was steam power, then electric power, then the internal combustion engine, then the semiconductor, then gene editing, and so on. Maybe there is limited opportunity within each area for productivity improvement
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x DUBBIO? NUOVE LINEE DI PRODOTTO?
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Maybe idea TFP is declining within every product line, but still not declining for the economy as a whole because we keep inventing new products.
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c
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For the U.S. economy as a whole, exponential growth rates in GDP per person since 1870 or in total factor productivity since the 1930s— which are related to the left side of equation (3)— are relatively stable or even declining. But measures of research effort— the right side of the equation— have grown tremendously. When applied to the aggregate data, our approach of looking at “idea TFP” is just another way of making this same point.
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x CONSIDERARE L INSIEME
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the overall trend is clear.
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3. Refining the Conceptual Framework
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T
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3.2. “Lab Equipment” Specifications
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T
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3.3. Heterogeneous Goods and the Lab Equipment Specification
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T
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3.4. Stepping on Toes
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t
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4. Moore’s Law
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T
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One of the key drivers of economic growth during the last half century is Moore’s Law: the empirical regularity that the number of transistors packed onto an integrated circuit serving as the central processing unit for a computer doubles approximately every two years.
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x COS È
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A doubling time of two years is equivalent to a constant exponential growth rate of 35 percent per year.
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c
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Many commentators note that Moore’s Law is not a law of nature but is instead a result of intense research effort: doubling the transistor density is often viewed as a goal
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x COME VEDERLA
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We measure research effort by deflating nominal R& D expenditures of key semiconductor firms by the nominal wage of high-skilled workers,
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x PROXY RD
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The striking fact, shown in Figure 4, is that research effort has risen by a factor of 25 since 1970. This massive increase occurs while the growth rate of chip density is more or less stable:
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x ESDITO
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TFP has fallen by this same factor of 25, an average rate of 7.3 percent per year.
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c
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4.1. Caveats
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5. Agricultural Crop Yields
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historical importance of agriculture
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Crop R& D is generally broken down into research on biological efficiency (crossbreeding and bioengineering), mechanization, management, protection and maintenance, and post-harvest (see, for example, Huffman and Evenson (2006)).
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x INNOVAZIONE AGRICOLA
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yields across these four crops roughly doubled between 1960 and 2015.
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x STUDIATI 4 RACCOLTI
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Yield growth has averaged around 1.5 percent per year since 1960 for these four crops, but with ample heterogeneity.
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c
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The effective number of researchers has grown sharply since 1969, rising by a factor that ranges from 3 to more than 25, depending on the crop and the research measure.
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x ADDETTI
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TFP has fallen sharply for agricultural yields:
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On average, idea TFP declines for crop yields by about 6 percent per year using the narrow definition of research and by about 4 percent per year using the broader definition.
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x ESITO
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6. Mortality and Life Expectancy
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T
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Our third collection of case studies examines the productivity of medical research.
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x TERZO SETTORE
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arithmetic growth provides a better description of the time path of life expectancy. Since 1950, U.S. life expectancy at birth has increased at a relatively stable rate of 1.8 years each decade, and life expectancy at age 65 has risen at 0.9 years per decade.
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x SPERANZA DI VITA
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“record female life expectancy”— the life expectancy of women in the country for which they live the longest— has risen at a remarkably steady rate of 2.4 years per decade ever since 1840.
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x DONNE SPERANZA
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6.1. New Molecular Entities
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T
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the number of new molecular entities (“ NMEs”) approved by the Food and Drug Administration. NMEs are new drugs,
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x PRIMA VARIABILE
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pharmaceutical R& D spending
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Research effort rises by a factor of 9, while idea TFP falls by a factor of 11 by 2007 before rising in recent years so that the overall decline by 2014 is a factor of 5. Over the entire period, research effort rises at an annual rate of 6.0 percent, while idea TFP falls at an annual rate of 3.5 percent.
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6.2. Mortality
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Idea TFP for our medical research applications is computed as the ratio of years of life saved to the number of publications.
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x PRODUTTIVITÀ IDEE
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Idea TFP rises until the mid 1980s and then falls. Overall, between 1975 and 2006, idea TFP for all cancers declines by a factor of 1.2 using all publications and a factor of 5.9 using clinical trials. The declines for breast cancer are even larger, as shown in Table 2.
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x ESITO SUL CANCRO
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7. Idea TFP in Firm-Level Data
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The case studies considered so far are useful for many reasons already explained. However, at the end of the day, they are just case studies, and one naturally wonders how representative they are of the broader economy.
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x SI PUÒ GENERALIZZARE?
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Declining idea TFP for corn or semiconductors could in this view simply reflect a further composition bias.
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c
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To help address these concerns, we turn to Compustat data on publicly-traded firms. The strength of these data is that they are more representative than the case studies, but of course they too have limitations.
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x A LIVELLO DI IMPRESA
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As a measure of the output of the idea production function, we use decadal averages of annual growth in sales revenue, market capitalization, and employment within each firm.
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x PROXY PRODUZIONE IDEE
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Why would growth in sales revenue, market cap, or employment be informative about a firm’s production of ideas? This approach follows a recent literature emphasizing precisely these links.
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c
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use of sales revenue or employment to measure fundamental productivity.
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To measure the research input, we use a firm’s spending on research and development from Compustat.
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x R D INPUT
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what we see in Table 3 are steady, rapid declines in firm-level idea TFP across all samples, at growth rates that range from -8.8% to -14.5% per year for multiple decades. Put differently, and reporting the results using sales revenue as a baseline, idea TFP declines by an average factor of 3.9 for firms that we can compare across only two decades, by a factor of 9.2 across firms we can compare across three decades, and by a factor of 40.3 across firms that we can compare across our entire 4 decade sample, between 1980 and 2015.16
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x ESITO
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c
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heterogeneity across firms is impressive and somewhat reminiscent of the heterogeneity we see in our case studies. Nevertheless, it is clear from these histograms that there is essentially no evidence that constant idea TFP is a good characterization of the firm-level data.
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x GENERALIZZAZIONE: PIÙ DIFFICILE AVERE IDEE
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8. Discussion
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T
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The evidence presented in this paper concerns the extent to which a constant level of research effort can generate constant exponential growth, either in the economy as a whole or within relatively narrow categories, such as a firm or a seed type or a health condition. We provide consistent evidence that the historical answer to this question is no:
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x RISULTATI OTTENUTI. RIPETIZIONE
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A natural question is whether or not these empirical patterns can be reproduced in a general equilibrium model of growth.
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x MODELLO GENERALE
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One way in which the overall interpretation of the evidence in this paper could be wrong is if there is indeed declining idea TFP in every sector, but the entire increase in aggregate R& D occurs in making quality/ productivity improvements for individual varieties.
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x QUANTITÀ CONOSCIUTA MA QUALITÀ?
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Nevertheless, this loophole is one that future research may wish to consider.
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c
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9. Conclusion
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T
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A key assumption of many endogenous growth models is that a constant number of researchers can generate constant exponential growth.
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x L ASSUNTO CONFUTATO
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idea TFP is falling sharply everywhere we look.
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TFP falls in half every 13 years
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ideas are getting harder and harder to find.
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U.S. must double the amount of research effort searching for new ideas every 13 years to offset the increased difficulty
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x IN ALTRI TERMINI
