When the government in 1989 started asking parents to provide the Social Security number of their putative day-care provider, claims for credits dropped markedly.)
Not all of the parents were able to provide Social Security numbers to the government.
mnli hypothesis: Not all of the parents were able to provide Social Security numbers to the government. premise: When the government in 1989 started asking parents to provide the Social Security number of their putative day-care provider, claims for credits dropped markedly.)