I have no quantitative evidence to support this, but I get the impression that prices are stickier in Ghana than in the United States.  My theory is that this is, ironically, because Ghana lacks sticker prices. 

Most people buy things in the market, and they just "know" the price.  If someone tries to charge them higher, they won't buy. My guess is that changing common knowledge of a price is actually a lot harder than just changing a sticker price. 

Could somebody do a study on this please? I recommend an RCT in isolated markets where you select half of the markets to go to sticker prices, where you provide the stickers.  Those markets operate with the stickers for a few months, where the control markets continue to operate without marked prices.  Then you introduce a price shock for, say, tomatoes, send out mystery shoppers, and see where prices change more quickly.  I would do it myself but I am busy.