When I was a kid, small cans of tuna were 8 ounces, cost about 8 cents and there was a little bit of oil in it. Mix in a little mayo and you could make a couple of sandwiches out of one can. I just noticed today that the small can of tuna is 5 ounces. When I opened it, there was closer to 2 ounces of water in there than one. I cut a slice of bread in half and made a half sandwich. There was enough for that.
So now, for 79 cents or a dollar, you get about 3 ounces of actual tuna.
At what point, I wonder, does the tuna content of a can of tuna become nutritionally insignificant?