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... surveys in high-income conutries show 3 to 5 cases per 1,000 of severe intellectural disability or cognitive disability,i.e, an iq below 55. estimates from developing contries, however, have found prevalence rates from 5 to as much as 22 per 1,000.

여기에서 왜 as many as가 아닌 as much as를 쓴건지 이해가 되지 않네요 ......
친절하고 자세한 답변 부탁드릴께요 ~~ .^^