Assertion: yak's number | /r/CapableOf | double in the period
Facets:
value: because of improved outlets for yak products
type: CAUSE
value: more than
type: OTHER
Source sentences:
text: Because of improved outlets for yak products, the number of yak more than doubled in every yak-raising area of China in the period 1950 - 1990, and in some cases increased by as much as two and a half-fold.