Cross-Domain Comparison

Act 6 Methods

The twelve ACT 6 Deep Dive chapters share a common analytical framework. The following metrics are used consistently across all domain analyses:

Four-Firm Concentration Ratio (CR4)

The combined patent share of the four largest assignees in a given domain-year. Higher values indicate greater organizational concentration. In the industrial organization literature, CR4 above 40% is typically classified as moderately concentrated and above 60% as highly concentrated (Bain, 1956; Shepherd & Shepherd, 2004).

Technology Diversity (Normalized Shannon Entropy)

Normalized Shannon entropy of the CPC subfield distribution within a domain: H/ln(N), where H = −Σ p_i ln(p_i) and N is the number of subfields. Values range from 0 (all patents in one subfield) to 1 (evenly distributed). Higher values indicate greater diversity across technology subfields.

Technology Velocity (Entry Cohort Productivity)

Average annual patents per assignee, computed by entry-decade cohort. Assignees are classified by the decade of their first patent in the domain. Higher velocity among later cohorts suggests that open-source diffusion or lower barriers to entry may be associated with faster patenting rates.

International Share

The percentage of domain patents whose primary inventor is located outside the United States. Based on the disambiguated location of the first-listed inventor.

Academic Share

The percentage of domain patents assigned to universities or research institutions, identified via the PatentsView assignee-type classification (types other than corporate or individual).