Whenever commercials compare products to the "leading national brand", how do we know the comparison is valid?

Question

How do consumers find out what the actual leading national brand is?

Answer 1

We don't, and it probably isn't. We don't even  know what 'leading' means. Don't take ads seriously; you should know that by age six.

Answer 2

If the ad runs nationally on one of the major broadcast networks (ABC, CBS, NBC, FOX) the network will have required proof of the statements.  The claims can be challenged by competitors and the network will not continue to run the ad if it is not truthful.  However, if the ad is running only on local stations then you have no such assurance.  (You have to pay close attention to when the network shows its logo and signs on and off to allow local commercials to air to know whether the ad ran on the network or on the station.)

In any case, you have to listen carefully and critically to the wording.  A statement can be perfectly accurate but still misleading.

"An independent research lab compared Gizmo brand to every other brand and you know what?!  Nobody's better than Gizmo, nobody!"  That's the kind of statement you'll hear and it sounds like they just claimed that Gizmo is better than the others -- but that's not what they said.  It's likely that the research could find no significant difference between the brands -- they're all the same.  Listen carefully to the claims they are making.