Wednesday, February 25, 2026 12:30 - 14:00

This event is both online and in person.

SAL 1.04, 1st Floor Conference Room, Sir Arthur Lewis Building, LSE, 32 Lincoln's Inn Fields, London WC2A 3PH

Online participants are welcome:
Please sign up to our mailinglist (seminar_macroiep) to receive event updates and a link to the seminar online.

About this event

How do inventors position themselves across the landscape of technological possibilities? Using US patent text from 1836 to 2023, we document that inventors are spreading out: contemporary inventions have become increasingly dissimilar over nearly two centuries. Patent interference data spanning 150 years corroborates this trend through declining rates of simultaneous invention. We develop a spatial competition model where inventors spread across expanding idea space to offset the rising burden of knowledge. Spreading reduces knowledge spillovers and raises adaptation costs, creating a drag on TFP growth while simultaneously boosting aggregate R&D spending through entry into new technological territories?spending that increases research inputs without raising productivity. Relating TFP and R&D growth to measured similarity, we validate the model's predictions and estimate key parameters. Spatial forces?inventors spreading across expanding idea space?account for approximately half of the long-run decline in US research productivity documented by Bloom et al. (2020), complementing traditional explanations (fishing out, burden of knowledge). Methodologically, we show that measuring technological similarity requires systematic validation: standard text analysis approaches can mislead, but our validation framework using expert assessments and human judgments identifies superior methods and provides validated similarity measures for innovation research.

Participants are expected to adhere to the CEP Events Code of Conduct.

Directions

This event will take place in SAL 1.04, 1st Floor Conference Room, Sir Arthur Lewis Building, LSE, 32 Lincoln's Inn Fields, London WC2A 3PH.

Online participants are welcome:
Please sign up to our mailinglist (seminar_macroiep) to receive event updates and a link to the seminar online.

The building is labelled SAL on the LSE campus map. You can also find us on Google Maps. For further information, go to contact us.

Trade and Urban Seminars are part of the CEP's Trade programme and Urban programme.