This article presents an empirical study based on all reported transformative use decisions in U.S. copyright history through January 1, 2017. Since Judge Leval coined the doctrine of transformative use in 1990, it has been gradually approaching total dominance in fair use jurisprudence, involved in 90% of all fair use decisions in recent years. More importantly, of all the dispositive decisions that upheld transformative use, 94% eventually led to a finding of fair use. The controlling effect is nowhere more evident than in the context of the four-factor test: A finding of transformative use overrides findings of commercial purpose and bad faith under factor one, renders irrelevant the issue of whether the original work is unpublished or creative under factor two, stretches the extent of copying permitted under factor three towards 100% verbatim re-production, and precludes the evidence on damage to the primary or derivative market under factor four even though there exists a well-functioning market for the use.

Although transformative use has harmonized fair use rhetoric, it falls short of streamlining fair use practice or increasing its predictability. Courts diverge widely on the meaning of transformative use. They have upheld the doctrine in favor of defendants upon a finding of physical transformation, purposive trans-formation, or neither. Transformative use is also prone to the problem of the slippery slope: courts start conservatively on uncontroversial cases and then ex-tend the doctrine bit by bit to fact patterns increasingly remote from the original context.
This article, albeit being descriptive in nature, does have a normative con-notation. Courts welcome transformative use not despite, but due to, its ambiguity, which is a flexible way to implement their intuitive judgments yet maintain the impression of stare decisis. However, the rhetorical harmony conceals the differences between a wide variety of policy concerns in dissimilar cases, invites casual references to precedents from factually unrelated contexts, and substitutes a mechanical exercise of physical or purposive transformation for an in-depth policy analysis that may provide clearer guidance for future cases.