Seems that they attempted to, but they can't definitively disprove it.
Basically, they couldn't find evidence, but they can't disprove the hypothesis and they can only tell from the year 2012. Thus, they can't see if stores let their advertising expire before that year or see the reviews stores had before advertising if they started before that.
Basically, they couldn't find evidence, but they can't disprove the hypothesis and they can only tell from the year 2012. Thus, they can't see if stores let their advertising expire before that year or see the reviews stores had before advertising if they started before that.