Kub, I think there are several parts to that weak demand; obviously overinvestment— in China, US, everywhere.
Add in the high commodities price hangover from all that demand (including oil of course),
Plus BIG MACRO stuff like the aging of the population in the big economies, increasing financialisation (whose only product is money), increasing automation that cuts out the cost of labor (and labor's income).
Then factor in the low real interest rates lever-pulling by central banks (US first) which affects inflation to an extent but also reduces returns on investments to zero or below eliminating the "penalty" on cash hoarding
And finally the Frack-Boom that has lowered the US oil imports has strengthened the dollar, and been more than offset by declining exports of other stuff.
All that inflating in an attempt to combat the Forces of Deflation.
I think down the road somewhere we (or someone) will look back and see the oughts as the last big hurrah before the long fizzle.
The legitimate object of government, is to do for a community of people, whatever they need to have done, but can not do, at all, or can not, so well do, for themselves -- in their separate, and individual capacities.
-- Abraham Lincoln, Fragment on Government (July 1, 1854)