Efficient Power Supplies

I just read an article at Tom’s about power supplies.
The most efficient one was a
Zippy PSM-6600P,
which had an efficiency of 80.3% under medium load, which was the best of the lot at that load.
This means it wasted the least amount of power, and generated the least amount of heat.
All of the power supplies were
ATX12V 2.0
power supplies.

It’s a long way fom the Apple II days, when I could comfortably tell my parents that it was okay to leave my computer on all the time, since it consumed less electricity than most light bulbs.
Now I would have to say it’s like leaving a low-powered microwave on all the time. :-/

I have the perception that as the high end marches on, the low end get more efficient over time.
Does anyone know if this is true?
It woud mean that a CPU at introduction consumes X Watts, and then after a few years, that is reduced by a significant percentage, say 50%?