My pants were lying to me

So I encountered a minor conundrum recently as my weight loss since I arrived has forced me to buy some new pants.  When I left the US I was in a hybrid phase where I had lost enough weight that some of my 38" waist pants were becoming nearly too loose, but I could only fit in a few certain pairs of 36" pants.  And since virtually no one makes 37" pants, I didn't have much in between.  So I ended up shipping over a large amount of 36" pants from my slimmer days that I figured I would eventually start fitting into.

But as I lost more weight and even the 36" pants started feeling loose, I decided to go out and buy some new pants for work.  Figuring I would start with 90 cm (the same as 36") and see if how much I have to go down with whatever brand I found (I know there is always some variability) I was shocked to find that the 36" pants I eventually found fit just fine.  And that this was true across all 4 of the brands I tried.  And that even those brands I tried but didn't buy (apparently skinny leg pants aren't just an option here, they are nearly the default, and those aren't comfortable for me) fit around my waist fine.

So out of curiousity I pulled out some of the pants that didn't really fit any more that I had brought over.  This included pants marked as both 38" and 36".  And in general, I found that they were all nearly at an inch bigger around the waistline (measured from where the flap over the zipper would lay to the end, which skipped the part that overlays the zipper area).  Most were actually over an inch bigger, which one pair of supposedly 38" pants actually having a waistline slightly over 40".  And nearly all of my supposedly 36" pants were 37" or bigger, with most being between 37" and 37.5".

So I have to wonder, are your pants lying to you too?  And why is that seemingly every pair of pants I brought from the US was significantly larger than advertised while that doesn't seem to be the case with the European brands I have bought here?  Have American's gotten so fat that our clothes retailers deliberately sell us clothes with incorrect labels in order to make us feel better about ourselves (and buy more of their brand)?