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Invention as a Combinatorial Process: Evidence from U.S. Patents
Hyejin Youn, Luis M. A. Bettencourt, Deborah Strumsky, Jose Lobo
TL;DR
Prior research has described invention as combinatorial but lacks a formal quantitative characterization of that process. The paper analyzes U.S. patent records through USPTO technology codes and finds that invention is driven mainly by combinations, with exploration and exploitation remaining invariant despite slowed creation of new capabilities. It concludes that novel combinations generate a practically infinite space of technological configurations.
Problem
Prior literature lacks a formal and quantitative characterization of the combinatorial process underpinning inventive activity.
Method
The paper treats patented inventions as carriers of technologies and uses USPTO technology codes to characterize invention combinatorially.
Results
Combination of technologies has been the major driver of invention, reflected in an invariant introduction of new technological combinations, while new technological functionalities play a minimal role once the system is mature.
Takeaways & Limitations
Despite a very reduced rate of new technology introduction, novel combinations generate a practically infinite space of technological configurations.
Takeaways & Limitations
Whether the technologies themselves restrict which combinations are tried is beyond the scope of the research.
Abstract
from arXiv · showhide
Invention has been commonly conceptualized as a search over a space of combinatorial possibilities. Despite the existence of a rich literature, spanning a variety of disciplines, elaborating on the recombinant nature of invention, we lack a formal and quantitative characterization of the combinatorial process underpinning inventive activity. Here we utilize U.S. patent records dating from 1790 to 2010 to formally characterize the invention as a combinatorial process. To do this we treat patented inventions as carriers of technologies and avail ourselves of the elaborate system of technology codes used by the U.S. Patent Office to classify the technologies responsible for an invention's novelty. We find that the combinatorial inventive process exhibits an invariant rate of "exploitation" (refinements of existing combinations of technologies) and "exploration" (the development of new technological combinations). This combinatorial dynamic contrasts sharply with the creation of new technological capabilities -- the building blocks to be combined -- which has significantly slowed down. We also find that notwithstanding the very reduced rate at which new technologies are introduced, the generation of novel technological combinations engenders a practically infinite space of technological configurations.
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1 Introduction
The introduction frames invention as a combinatorial process but identifies a lack of formal quantitative characterization. Using U.S. patent records and technology codes, the paper studies how combinations, new capabilities, and search dynamics shape inventive novelty.
- Existing discussions of combinatorial invention rely largely on case studies and historical analyses rather than quantitative characterization.
- The paper uses U.S. patent records as carriers of technologies and USPTO technology codes to identify capabilities and combinations.
- The study asks how prevalent combination and recombination are, how new technological functionalities fuel them, and what the combinatorial process is like.
- A formal description enables investigation of how technology space is searched and how search generates different types of inventive novelty.
- The empirical record spans over 200 years of inventive activity and reveals regularities in generating inventive novelty.
2 Patents as Footprints of Invention
Patents provide a documentary trail for studying inventions as bundles of technological capabilities. USPTO classifications encode novelty-relevant technologies and distinguish new capabilities from new combinations of existing ones.
- Patented inventions leave a documentary trail that enables systematic study of invention processes.
- A patent covers one invention consisting of several closely related and indivisible technologies that accomplish a specified task.
- The “unity of invention” principle makes patented inventions plausible units for discretizing technologies into a few distinct components.
- USPTO technology codes classify the technologies responsible for an invention’s novelty and capture new technologies or unprecedented combinations of existing capabilities.
- The available technology codes describe current technological capabilities, while examiners choose existing or new codes for each application.
- There are currently 474 technology classes and approximately 161,000 technology codes, with no limit on codes assigned to a patent.
3 Invention as a Combinatorial Process
U.S. patent records show invention increasingly proceeds by recombining existing technologies, even as new technology codes arrive more slowly. Across roughly two centuries, new combinations continue to expand the space of possible technological configurations.
- 77% of patents granted between 1790 and 2010 use combinations of at least two technology codes.
- Patents, technology codes, and code combinations grew exponentially during the first 80 years of the record.
- After about 1870, technology-code growth slowed significantly while patents and combinations continued growing together.
- New combinations increased linearly with patents, while new technology codes were introduced at a much reduced rate.
- As inventions combined more codes, the possible configuration space continued expanding despite slower introduction of new technology codes.
- ΔC/ΔP remained approximately invariant at 0.6, indicating that about 60% of inventions introduced new combinations and about 40% reused existing ones.
4 Invention: Broad or Narrow Combinations?
The paper measures technological distance through USPTO classes, distinguishing combinations assembled within one class from those spanning different classes. The share of narrow combinations varies over time, with a postwar decline followed by a later increase.
- Technological combinations are categorized as narrow or broad using whether their codes share a USPTO technology class.
- Narrow combinations use multiple codes from the same technology class, whereas broad combinations bring together codes from different classes.
- About 44% of multiple-code patents were narrow across the full 200-year period.
- Before 1930, about half of technological combinations were narrow; after World War II, this proportion fell to about 30%.
- From around 1970, the narrow-combination share increased and reached about 50%, alongside a dramatic rise in patenting.
5 Discussion
Patent technology codes enable systematic empirical study of invention as technological recombination. The results identify combination, refinement, and exploration as central features of invention, while new technological functionalities play a minimal role in mature systems.
- Empirical approach: Patent technology codes identify distinct technologies and their combinations, enabling systematic empirical study of the combinatorics of invention.Patented inventions are assessed by the technologies combined within them rather than by cited prior art.
- Combinatorial invention: The combination of technologies is the major driver of invention, with patented inventions introducing new technological combinations at an invariant rate.This finding characterizes invention as a persistent combinatorial process.
- Technological capabilities: New technological functionalities play a minimal role in fueling invention once the system is mature, whereas tinkering, gradual modification, and refinement remain important.The contrast is between creating new building blocks and modifying existing technological combinations.
- Novelty and recombination: Novelty stems from combining technologies rather than using new technologies per se, with slightly more inventive combinations being previously unseen than reused.Inventions combine related technologies as often as technologies from distinct domains.
- Exploration and exploitation: Novel and interdisciplinary combinations represent exploration, while reuse and integration of similar technologies represent exploitation.The authors describe inventive search as positioned halfway between exploration and exploitation, potentially reflecting a nearly optimal strategy.
- Technological evolution: Patent records can support quantitative comparisons with biological evolution because technological invention is also a generative combinatorial search process.The discussion highlights possible parallels involving building blocks, historical path dependence, and guided exploration.