How Do You Know That is Really 15lb Test?

Have you ever wondered how some brands of fishing line seem to be different diameter than other brands of the same pound test?  I have.  I know of some brands that are consistently thicker than others, but the label always says a certain size.  I have always wondered just how this is possible.  There are some that say fishing line companies are dishonest with their packaging.  Really, there is no way to tell what pound line is what, besides looking at the package.  Sure you can look at the actual diameter, but that takes a little more work.  A growing movement in Europe is the EFTTA (European  Fishing Tackle Trade Association)  Line Charter that is promising to make sure all companies have the same standards of line sizing.  Maybe we need something like that here in America.  In my opinion, it would really help.  Some of the biggest names in fishing (Pure Fishing, Shimano, Daiwa, Sufix, etc) have signed the charter and it is gaining momentum and publicity in magazines like Angling International.  What do you think?  Is this that big of a deal?