Guages of wire, like same of metal, do not change, they are standards.
The use of #12 Cu wire is prohibited under the Ont electrical code due to
the added stresses the thicker wire places on the terminals and screws of
the outlets.
Prob the same where you live. This is one instance where overdoing is
underdoing with a result in No Insurance Coverage.
When #12 or #10 is used on a branch circuit, the device must be rated
commercial and applicable for the wire used.
"SQLit" wrote in message
...

"Nexus7" wrote in message
oups.com...
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.

I have been in the "trade" for 35 years, American Wire Gauge has not
changed
it that time. 12 is 12 and 14 is 14. What has changed in romex is that
some manufactures A LONG TIME AGO made romex with 12 or 14 conductors and
a
reduced ground ~16awg. These cables were produced before I started buying
wire.