I did a search and there are threads about this, but they didn’t receive a lot of attention. I used to measure with a thin headphone cord, and I recently starting using a paper ruler. Since using the paper ruler, my girth measurement appears smaller by around half an inch. I didn’t lose girth, but the thickness of the headphone cord made the measurement larger than it already was. Just a warning to all of you measuring girth, for a true measurement use something paper thin.