Batia Laufer is an Israeli applied linguist and Professor Emerita at the University of Haifa, where she has spent her career researching second-language vocabulary acquisition, lexicography, cross-linguistic influence, reading, and testing. Her work sits at the centre of nearly every consequential debate about lexical coverage and vocabulary measurement in the past three decades.
Laufer's 1989 chapter "What percentage of text-lexis is necessary for comprehension?" introduced the 95 percent coverage figure that became the field's first widely cited threshold for adequate text comprehension. With Geke Ravenhorst-Kalovski she revisited the evidence in 2010, proposing two thresholds: a minimal one at 95 percent (4,000–5,000 word families) and an optimal one at 98 percent (around 8,000 word families). With Paul Nation she developed the Lexical Frequency Profile and the Productive Vocabulary Levels Test, instruments that materials writers and assessment teams still rely on.