Assertion: duck's number | /r/CapableOf | cycle over last 50 years
Facets:
value: between about 5 million
type: OTHER
value: between 11 million
type: LOCATION
Source sentences:
text: Their numbers increase during wet periods and decline when there are droughts in the middle of the continent—over the last 50 years their estimated numbers have cycled between about 5 million and 11 million.