Nexus7 wrote:
I've come across some wire that is probably 30 years old and is marked
14 gauge. The minimum gauge I want snaking around the house is 12
gauge, so I was about to pull it out when I noticed that the copper is
about as thick as new 12 gauge (and thicker than new 14 gauge). Is the
copper thinner now because of improvements in the manufacturing
process, or something? Is the wire rated by thickness or by current
carrying capacity? If it is current carrying capacity, then are they
using thinner wire because newer copper is a better conductor? This
isn't the plastic insulation I'm talking about, it's about the copper
itself.

The responses to your question include a lot of
nonsense and extraneous discussion. The answer is
that wire gauges are the same, unless you go back
a long way. Like someone said, put a gauge on
both wires. It could be that one of the wires is
labeled wrong. The gauge will tell the story.