GMO has modeled momentum and value as two key variables for 33 years.

The claim is that GMO (Grantham's firm) used momentum and value as two key variables in its models from about 1979, 33 years before December 2012. TRUE: GMO histories, publications or credible accounts show it used both value and momentum as core model variables starting around 1977–1981. MOSTLY TRUE: both were core variables but use began about 3–6 years later or earlier than 1979, or one was added a few years after the other. MIXED: GMO has long used one of the two (e.g. value) as a key variable, but the other was adopted much later. MOSTLY FALSE: both were used, but only from the 1990s or later. FALSE: GMO did not treat momentum and value as key model variables, or began only shortly before 2012.

Set before the research began.

1. E1 Hancock [2010-03] Momentum – a Contrarian Case for Following the Herd GMO (white paper, reposted on Scribd) · March 2010 Own record

   “As noted earlier, GMO started using momentum strategies in the U.S. in the late 1980s based on patterns observed from returns in the 1970s and 1980s.”

2. E2 Career Risk and Conviction: Inside Jeremy Grantham's Investment Philosophy Robert Huebscher (Substack) · 23 March 2026

   “Eventually, he settled on a model that focused on value and quality. Value meant buying stocks with low price-to-book ratios, and quality focused on high and stable profits.”

3. E3 2014 Money Manager Lifetime Achievement Award Winner: Jeremy Grantham Institutional Investor · 8 May 2014

   “GMO, as the $117 billion-in-assets, Boston-based firm is known today, was a pioneer in international investing, quantitative strategies and tactical asset allocation, expanding beyond its original value-oriented-equity focus to include growth funds, fixed income and emerging markets.”

4. E4 GMO LLC Wikipedia · 13 May 2023

   “The three all were portfolio managers and GMO was launched as a conservative, value-oriented money management shop although it has expanded since.”

Independent sources say GMO began as a value-oriented manager (E3, E4), and E2 describes a model built on value and quality. That supports value as a long-standing key variable. However, GMO's own 2010 white paper says it "started using momentum strategies in the U.S. in the late 1980s" (E1). That is roughly 8–10 years after the 1979 start the claim implies, which is longer than the 3–6 year gap the criteria allow for mostly true. Under the criteria, value is supported as an early key variable [E3][E4], while the only evidence on momentum dates GMO's U.S. momentum strategies to the late 1980s [E1], so the claim resolves as mixed.