Over the past five years, the price gap between name-brand cereals and less expensive store-brand cereals has become so wide that consumers have been switching increasingly to store brands despite the name brands' reputation for better quality. To attract these consumers back, several manufacturers of name-brand cereals plan to narrow the price gap between their cereals and store brands to less than what it was five years ago.

Which of the following, if true, most seriously calls into question the likelihood that the manufacturers' plan will succeed in attracting back a large percentage of consumers who have switched to store brands?

【选项】Total annual sales of cereals-including both name-brand and store-brand cereals-have not increased significantly over the past five years.