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Jean-Baptiste Michel helped develop quantitative analysis of large digitized text collections. He is a lead and corresponding author of the study introducing culturomics, which examined changes in language and recorded culture using a large book corpus.^[ref]

A central measurement is relative word frequency: occurrences of a word or phrase in books assigned to a year are normalized by the number of corresponding word sequences in that year's corpus. A raw count can rise merely because more text was digitized. For an elementary illustration, one hundred occurrences among a million tokens and two hundred among four million tokens represent a halving of relative frequency, despite the doubled count.

The data measure the contents of a sampled textual archive. Book selection, date metadata and recognition errors can affect the apparent history of a word; frequency is not a direct measurement of how many people held a belief. The study's contribution was to make large-scale temporal comparisons computationally tractable and quantitatively inspectable, while exposing the importance of the observation process.^[ref]

Joe Jackson coauthored the 2007 quantitative study of English irregular-verb regularization. Its byline identifies the author with Harvard's Program for Evolutionary Dynamics.^[ref]

The authors tracked a historical cohort of irregular verbs and related survival of irregular forms to word frequency. This illustrates survival analysis applied to cultural transmission: the object being lost is a linguistic form. The estimated regularization rate describes an aggregate pattern, without implying that all low-frequency verbs change together.^[ref]

Tina Tang coauthored the 2007 study relating historical changes in English irregular verbs to word frequency. Its byline identifies the author with Harvard's Program for Evolutionary Dynamics.^[ref]

The authors found an approximate square-root relation between frequency and irregular-verb half-life. A hundredfold increase in frequency corresponds to a tenfold increase in half-life under that fitted relation. It describes a statistical pattern across the studied verbs, rather than a schedule for when an individual verb must change.^[ref]