As the price of cocoa rose after 1973, so the cocoa content in chocolate went down as manufacturers tried to avoid passing price increases on to customers in order to keep up sales. They found ways to use less cocoa: Firstly, by promoting confectionery with filled cheaper centres which meant fewer solid chocolate bars. Secondly, by using a proportion of other cheaper vegetable fats instead of cocoa butter.
Even when the cocoa prices fell it took time for the ingredients ratio to improve as, having altered their recipes, the manufacturers were not inclined to return to higher cocoa quantities. Although in the 1990s, cocoa prices were at their lowest ever; the ingredient ratios have never returned to their previous levels. The change in chocolate-eating habits as a result of the 1970s constraints meant that people have adapted to eating more filled centres, especially cereal centres, and improvements in processing worked against the return to a high proportion of cocoa to chocolate.