The paragraph is followed by an incomplete phrase or sentence which summarizes the main idea of the paragraph. Choose the missing words of the phrase or sentence.

Of the approximately 21 million American children under age five in 1995 who were not already in preschool, about 40% were cared for by parents, 31% by child-care centers, 21% by relatives, and 14% by family day-care homes. Since 1965 the percentage of children in child care centers has risen from 6% to 31 %.
（） numbers of children in child care centers.