, Volume 90, Issue 2, pp 407-427

First online:

A forward diversity index

  • Stephen CarleyAffiliated withSchool of Public Policy, Georgia Institute of Technology Email author 
  • , Alan L. PorterAffiliated withTechnology Policy and Assessment Center, Georgia Institute of TechnologySearch Technology Inc.

Rent the article at a discount

Rent now

* Final gross prices may vary according to local VAT.

Get Access


We introduce an indicator to measure the diffusion of scientific research. Consistent with Stirling’s 3-factor diversity model, the diffusion score captures not only variety and balance, but also disparity among citing article cohorts. We apply it to benchmark article samples from six 1995 Web of Science subject categories (SCs) to trace trends in knowledge diffusion over time since publication. Findings indicate that, for most SCs, diffusion scores steadily increase with time. Mathematics is an outlier. We employ a typology of citation trends among benchmark SCs and correlate this with diffusion scores. We also find that self-cites do not, in most cases, significantly influence diffusion scores.


Knowledge diffusion Integration score Diffusion score Citation patterns Self-citations Subject category behavior