Assertion: guinea pig | /r/ObjectUse | used in 1960
Facets:
value: for research
type: PURPOSE
value: annually
type: TEMPORAL
Source sentences:
text: Guinea pigs remained popular laboratory animals until the later 20th century: about 2.5 million guinea pigs were used annually in the U.S. for research in the 1960s, but that total decreased to about 375,000 by the mid-1990s.