Shrinking package sizes without shrinking prices is one of the little tricks manufacturers use to fool consumers into believing they are still getting the same deal at the same price. It is one of my pet peeves because it assumes that the consumer is too stupid to figure out what is happening.
The most striking example of this practice has been with Dawn dishwashing detergent. One year ago the small size, which would go on sale for 99 cents, was 13 ounces. Six months ago the size reduced to 11 ounces. Now the small size is 9 ounces. I have also seen the sale price going up to over a dollar in some stores.
Keep doing the math. If the size of this product keeps reducing it may become less expensive to buy a larger size. Personally, I am not dedicated to just one brand, so I'll just switch to a detergent manufacturer that is a little less deceptive.