The composition of patents tells the story of technological change. Over five decades, the balance of innovation has shifted dramatically from traditional industries like chemistry and mechanical engineering toward electrical engineering and computing.
WIPO Technology Sectors Over Time
Patent grants by WIPO sector (primary classification), 1976-2025.
The 1990s crossover where electrical engineering surpassed chemistry represents one of the most significant structural shifts in the history of patenting, driven by the computing and telecommunications revolutions.
Electrical engineering has seen explosive growth, driven by the computing, telecommunications, and semiconductor revolutions. Chemistry, once the dominant sector, has grown more slowly. Mechanical engineering and instruments have maintained steady contributions.
CPC Technology Sections: Share Over Time
Share of utility patents by CPC section (primary classification). Sections: A=Human Necessities, B=Operations, C=Chemistry, D=Textiles, E=Construction, F=Mechanical, G=Physics, H=Electricity.
The 100% stacked view makes relative shifts visible. Digital technology sections (G, H) have gained nearly 18 percentage points of share over five decades, while chemistry and operations have contracted proportionally.
The 100% stacked view reveals the relative shifts more clearly. Section H (Electricity) and G (Physics) -- which cover computing, semiconductors, optics, and measurement -- have grown from roughly 30% of patents in the 1970s to over 45% today. Meanwhile, traditional sections like C (Chemistry) and B (Operations) have seen their share decline.
Structural Change
The magnitude of these structural shifts is striking. The fastest-growing classes show increases of several hundred percent, while declining classes have contracted by similar margins. These are not small adjustments at the margin -- they represent fundamental reorientation of inventive activity.
Technology Diversity Index
1 minus the Herfindahl-Hirschman Index of CPC section concentration. Higher values indicate more diverse technology output.
Despite the explosive growth of electrical engineering, the patent system's technology mix has not narrowed dramatically. Innovation continues broadly across established fields.
The Half-Life of Technology
How quickly does a technology become obsolete? By measuring when a patent receives the bulk of its forward citations, we can estimate the "half-life" of knowledge in each technology area — the time it takes for 50% of all citations to accumulate. Shorter half-lives indicate rapidly evolving fields; longer ones suggest foundational knowledge with lasting relevance.
Citation Decay Curves by Technology Area
Distribution of forward citations by years after grant. Each line shows what percentage of a technology area's total citations arrive in each year.
Fast-moving fields like computing (H) and physics (G) have short citation half-lives, meaning knowledge becomes obsolete quickly. Chemistry and pharma innovations remain relevant for much longer.
Technology Life Cycle S-Curves
Fitting logistic S-curves to cumulative patent counts by CPC section reveals where each technology sits in its innovation lifecycle. Mature technologies like mechanical engineering and chemistry show slowing growth rates, while computing-related sections continue their steep ascent.
Technology Maturity by CPC Section
Percentage of estimated carrying capacity (K) reached by each CPC section, based on logistic S-curve fit to cumulative patent counts 1976–2025.
Textiles (D) and Fixed Constructions (E) have reached over 70% of their estimated carrying capacity, suggesting maturation. Physics (G) and Electricity (H) — home to computing, AI, and semiconductors — still have significant room to grow.
Having explored which technologies have driven the patent explosion, the next chapter asks who is doing the patenting. The shift from chemistry to digital technology has reshaped not just what gets patented but which organizations dominate -- from American industrial conglomerates to Asian electronics giants.
Technology classifications use the primary CPC section (sequence 0) for each patent and WIPO technology fields mapped from IPC codes. Technology half-life is computed as the time until 50% of cumulative forward citations are received, based on patents granted 1976-2010 with citations tracked through 2025.