Nearly 12 percent of convenience stores run by major operators have opted against around-the-clock operations, citing a worker shortage and declining late-night demand, a Kyodo News survey showed Monday. The survey, conducted in April and replied to by all seven major convenience chain operators except Yamazaki Baking Co., showed that around 6,400 of the 55,000 convenience stores in the country were operating with shortened business hours between February and April. Some stores have accelerated the introduction of unmanned cash registers to cope with the intensifying labor shortage. Industry l…