## Abstract

Categorization is an important phenomenon in science and society, and

classification systems reflect the mesoscale organization of knowledge.

The Yule-Simon-Naranan model, which assumes exponential growth of the

number of categories and exponential growth of individual categories

predicts a power law (Pareto) size distribution, and a power law

size-rank relation (Zipf’s law). However, the size distribution of

patent subclasses departs from a pure power law, and is shown to be

closer to a shifted power law. At a higher aggregation level (patent

classes), the rank-size relation deviates even more from a pure power

law, and is shown to be closer to a generalized beta curve. These

patterns can be explained by assuming a shifted exponential growth of

individual categories to obtain a shifted power law size distribution

(for subclasses), and by assuming an asymmetric logistic growth of the

number of categories to obtain a generalized beta size-rank relationship

(for classes). This may suggest a shift towards incremental more than

radical innovation.

classification systems reflect the mesoscale organization of knowledge.

The Yule-Simon-Naranan model, which assumes exponential growth of the

number of categories and exponential growth of individual categories

predicts a power law (Pareto) size distribution, and a power law

size-rank relation (Zipf’s law). However, the size distribution of

patent subclasses departs from a pure power law, and is shown to be

closer to a shifted power law. At a higher aggregation level (patent

classes), the rank-size relation deviates even more from a pure power

law, and is shown to be closer to a generalized beta curve. These

patterns can be explained by assuming a shifted exponential growth of

individual categories to obtain a shifted power law size distribution

(for subclasses), and by assuming an asymmetric logistic growth of the

number of categories to obtain a generalized beta size-rank relationship

(for classes). This may suggest a shift towards incremental more than

radical innovation.

Original language | English |
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Place of Publication | Maastricht |

Publisher | UNU-MERIT |

Publication status | Published - 1 Jan 2014 |

### Publication series

Series | UNU-MERIT Working Papers |
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Number | 060 |