Investment = Savings (This is an identity in economics just two different names for the same thing.) Productivity = (Investment - [inventories, replacement of used up capital goods and write-offs of bad investments])/population. Breakeven savings has a SWAG of about 6%. I suspect the actual number is higher but like the RDA minimums that you can get by with in terms of vitamins without greatly increasing your number of sick days it is minimum that prevents immediate harm. Going below 6% savings for decades caused a gutting of employment first in manufacturing, then in construction in 2007 and finance 2008-9. Savings = Income - (Consumption, Taxes and Debt service [amortization as well as interest and liens upon collateral]) So we can continue in the race to the bottom to end up with Chinese wages and pollution by means of stimulus packages or we can go with austerity. Which way do you want to go?