I did a little Googling and came up with:
2009 Ford Focus wt. = 2623 lbs.
2008 Honda Fit = 2512 lbs.
1985 Honda CRX HF = 1713 lbs.
So, “less than half” is a bit of a stretch, but, nonetheless, your point is well taken. All these nits who think the auto companies can just increase fuel economy at will are not taking all factors into account.
At this point, what with all the regulations, the auto makers have run out of aero and engine tricks. The last straw was the Euro-mandated and US-recommended high hoodlines “for pedestrian safety”. It is almost impossible to get something with a mandated high bluff front to get better fuel economy than something small and low slung, yet that’s exactly what the government wants companies to do.
Even before then, all the makers were sounding off about running out of things they could do for fuel efficiency while keeping cars affordable.
There is a story running around about Honda taking a look at remaking the CRX idea in a manner that would get the 55-60mpg of the original but meet modern standards. Turns out they’d have to make it mostly out of carbon fiber and titanium and it would cost $65,000 a copy.
Honda shelved the plans.