I worked at McDonald’s a decade prior to that, and they were 10:1 then, too. I think it’s possible and maybe likely some other chains might have switched from being 8:1 to 10:1 since the market leaders already had that size. There are much better examples though than some isolated regional player’s beef patty sizes.
We used to buy half gallons and gallons of ice cream. Brands started selling 60 or 62 ounces instead of 64. Over the years, it’s gotten to where some brands sell 48 ounces - three pints - instead of 64.
Breakfast cereals have had similar shrinking sizes.
Breakfast cereal boxes have gotten so small, it's ridiculous. They might as well label the package "Fun Size" since it's clearly not "Full Size".
Shrinkflation is to me the best example of why pure short-term-ism is a cancer. The first jackass to do it, say by taking a soup can of 16 ounces and adjusting it to 15.75oz, it boosted the profits that quarter. Mathematically, we could keep asymptotically shaving the size by 1.6% every couple years forever, but IRL that won't work because the amounts needed to be shaved would get so small as to not have the cost savings effect (or even be possible to precisely measure). So in reality the amounts need to be more like an actual quarter or half ounce at a time. So at some point the soup can, the candy bar, etc. would become so small that with one more shrink, people will recognize that it can't even feed one person, and at that point, all the "value" that was extracted by the previous CEOs to goose their stock price short term will be exhausted, and they'll have to move on to watering it down or whatever. But our packages will stay that idiotic minimum size forever.