Monthly Archives: April 2013

Patents, Super Patents and Innovation at Regional Level

Related Variety, Unrelated Variety and Technological Breakthroughs: An analysis of U.S. state-level patenting

By Carolina Castaldi  (, School of Innovation Sciences, Eindhoven University of Technology

Koen Frenken, ( School of Innovation Sciences, Eindhoven University of Technology

Bart Los, (, Groningen Growth and Development Centre



We investigate how variety affects the innovation output of a region. Borrowing arguments from theories of recombinant innovation, we expect that related variety will enhance innovation as related technologies are more easily recombined into a new technology. However, we also expect that unrelated variety enhances technological breakthroughs, since radical innovation often stems from connecting previously unrelated technologies opening up whole new functionalities and applications. Using patent data for US states in the period 1977-1999 and associated citation data, we find evidence for both hypotheses. Our study thus sheds a new and critical light on the related-variety hypothesis in economic geography.

Review by Anna Missiaia

This paper by Carolina Castaldi, Koen Frenken and Bart Los was distributed by NEP-HIS on 30-03-2013. The paper is not, strictly speaking, an economic or business history paper. However, it provides some very interesting insights on how technological innovation and technological breakthroughs happen. This is a large and expanding field in economic history and on-going research on the economics of innovation, I believe, can be of interest to many of our readers.

Professor Butts and the Self-Operating Napkin: The “Self-Operating Napkin” is activated when the soup spoon (A) is raised to mouth, pulling string (B) and thereby jerking ladle (C) which throws cracker (D) past parrot (E). Parrot jumps after cracker and perch (F) tilts, upsetting seeds (G) into pail (H). Extra weight in pail pulls cord (I), which opens and lights automatic cigar lighter (J), setting off skyrocket (K) which causes sickle (L) to cut string (M) and allow pendulum with attached napkin to swing back and forth, thereby wiping chin. (Rube Goldberg, 1918).

The paper is concerned with the study of how innovation in a region is affected by the connections within its sectors in terms of shared technological competences. The term “variety” conveys this concept. The authors differentiate in two types of variety: related and unrelated variety. The former describes the connection among sectors that are complementary in terms on competences and can easily exchange technological knowledge. Unrelated variety, on the other hand, steams from sectors that do not appear to have complementary technology.

These two different types of variety are useful to distinguish for their effects on innovation. Related variety supports productivity and employment growth at regional level. However, unrelated variety is the one that causes technological breakthroughs, as it brings a completely new type of technology into a sector. In a subsequent stage, unrelated variety becomes related, being absorbed by the new sector.

The paper keeps these two types of variety separate and tests for their effects. The authors use patent data for US states in the period 1977-1999. The methodology implies regressing the number of patents as a proxy for innovation, on measures of related variety, unrelated variety, research and development investment, time trend and state fixed effects.  Variety is measured by looking at the dispersion of the classification of patents within and between technological classes of the patents. The paper also proposes two different regressions, one using the total number of patents as dependent variable and one using the share of superstar patents, which represent patents that lead to breakthrough technologies. Superstar patents are distinguished from “regular” patents according to the distribution of their citations: superstar patents have a fat tail, meaning that they are cited more in later stages of their development compared to regular patents.

A nice contribution of this paper is to measure super patents through their statistical distribution of their citations instead of relying on superimposed criteria such as being on the top 1% or 5% of the citations. The idea here is to distinguish between general innovation (regular patents) and breakthrough innovation (superstar patents). Theory predicts that regular patents will be positively affected by related variety, producing general innovation, while superstar patents will be positively correlated with unrelated variety, producing breakthrough innovation. The empirical analysis nicely confirms the theory.

Technological progress is said to resemble a flight of stairs

The possible shortcomings of the paper are related to the role of geography in the analysis. The sample is at US state level and the underlying implication is that variety in the state affects the number of patents registered in it. There could be, under this assumptions, some issues of spatial dependence. The authors touch upon this point in two parts of the paper: in the methodology section they explain that superstar patents tend to cluster in fewer states that general patents and this pattern requires a different approach for the two types of patents. It would be useful if this issue could be elaborated further by the authors in a future version of the paper.

As for the possible spatial dependence effect among explanatory variables, the authors try to control for the fact that R&D in one state could affect the patent output of neighboring states as well. They construct an adjacency matrix to capture the effect of the R&D effort of neighboring states.

The conclusion is that the analysis is robust to spatial dependence. In spite of this robustness check for spatial dependence, some concerns remain. Restricting the R&D effect only to neighboring states could be a limit, as the effect could not only go through physical proximity, but also through other types of connections: for example, the same firm could have different branches in different non-adjacent states, leading to an influence not captured by the adjacency matrix.

In short, this paper provides a very interesting insight on how two types of innovations can arise as measured by patent citations at regional level. The results are consistent with the theory and could be useful to future research in historical perspective. A further improvement of the paper could be to conduct more robustness check on the geographical aspects of these results, especially expanding them to non-adjacent states.

Images of the future technology – The Jetsons, 1962

The Origins of the Modern Concept of Money

French economists and the purchasing power of money

by Alain Béraud (, THéorie Economique, Modélisation et Applications (THEMA), Université de Cergy-Pontoise (France)


When French economists read The Purchasing Power of Money, they were primarily interested in the equation of exchange and the reformulation that Fisher proposed regarding the quantity theory of money. This reading led them to ponder the meaning that should be given to this theory and to study its empirical significance. Some of them, namely Rueff and Divisia, went further still and considered Fisher’s work as a starting point for their own analyses, which were related in particular to the monetary index, the integration of money into general equilibrium theory and the analysis of monetary phenomena in an open economy.

Keywords: quantity theory of money; price index; theory of purchasing power parity; marginal utility of money; integration of money into general equilibrium.


Review by Bernardo Bátiz-Lazo

This paper was circulated by NEP-HIS on 2013-03-30. Alain Béraud, its author, offers a detailed account of how many French economist criticised Irving Fisher’s (1867–1947) quantity theory of money while others supported it. In particular, he explores the extent to which Firsher’s ideas appear within the work of two great French economists, namely François Divisia (1889-1964) and Jacques Rueff (1896-1978).

Alain Béraud – Professeur de Sciences Économiques
(Université de Cergy-Pontoise)

Fisher’s formulation of the equation of exchange (where the total price of commodities sold equals the total value of the money that was given in exchange) is now part and parcel of every undergraduate programme in economics. It is integral and fundamental to the current understanding of macroeconomic management. Given this plus the rise of digital payments, mobile-phone wallets and crypto-currencies like Bitcoin, it is important to remember and indeed timely, to have an in depth discussion about how our conception of money – then measured as notes and coins – came to be and how it was shaped by dissenting views. In this regard says Béraud:

From the time of its publication through to the 1930s, The Purchasing Power of Money was the reference work for French economists who interpreted it as the modern, rigorous version of quantity theory. But this theory was hardly popular. It is therefore not surprising that many French economists, while recognising its merits, fiercely criticised it. It was only in the 1920s that Rueff and Divisia, both graduates of the École Polytechnique where they had been students of Clément Colson, used this book to develop their own analyses of monetary phenomena. Here, I have defended the idea that their contributions were certainly original but were nonetheless based on ideas that Fisher had supported.

Front of French frank coin (1996), commemorating the life of Jacques Rueff

As noted above, through his narrative Béraud compares and contrasts how the work of Fisher was incorporated into the ideas of French economists. He also offers a rich discussion of the reasons why there was dissent and why many took exception and actively criticised Fisher’s work.

The picture that emerges from Béraud’s work allows us to see how economist of the early 20th century on both sides of the Atlantic are engaging in a type of debate that now dominates the discipline, namely highly quantitative and empirically based. Something that, I thought, only took place after World War II – and thus, happy to be set straight. Moreover, this sort of debate was something that, according to Walter Friedman’s brief biography of Fisher, characterised Fisher’s early contributions to our understanding of macroeconomic phenomena. However, we are not provided by Béraud with enough detail to ascertain if a debate with such characteristics was widespread in France or whether it is Béraud’s reconfiguration of the debate between monetary factors and prices, that which leads us to emphasise its quantitative, formal, empirical aspects.

It was also interesting to know that the contemporary discussion of Fisher’s ideas was hampered by lack of available data. For instance, Béraud notes that at this point in time: “data on bank deposits [was unavialble]. Only some establishments published monthly statements.” Here, in my view, some more context as to how and when such measures came to be mainstream and a brief reference to the overall construction of macroeconomic statistics in France would have given a bit more sense of perspective to the discussion.

In the same vein, I would have liked, as a manner of introduction, some context as to why, how relevant and how widespread the debate of Fisher’s ideas was in France during the interwar period. It seems French economists are very concerned with determining exchange rates and the future of the Gold Standard at the end of the First World War. But this is only mentioned in passing. For the international reader it would have also been helpful to have an introduction as to the broad configuration of French economists groups or lines of work at this point in time.

But for all my comments and on balance, this paper makes an interesting read.

François Divisia (1889-1964) – a founding member of the “Econometric Society”