Actually Tonn it is proven that savings create far more economic growth than spending. When you save your money the banks can then lend it or use it for investment capital. It does not produce e direct profit which is what most people seem to concentrate on but it does create economic stimulus allowing for new business to open and be viable.
Hmm, well it's only about 1/8 of my savings that are in a bank. But really, to use the example in this thread, let's say my province, PEI, lowered the tax rates. Of the fraction of new take home income I receive, the savings are going into a variety of different funds managed by my financial planners, and into a savings account from a national bank that isn't technically even in the province I reside in. How much of that is actually going to spur economic development in PEI? I don't know, but I would guess it's peanuts compared to if I did actually spend it all at local businesses.
Also, I would imagine bank leveraged growth from my savings account would happen on longer time scales than spending money at a furniture store, or buying a boat from the local marine shop. Capital expenditures in the company I work for take a hell of a lot longer to approve than a purchase order.
I'd think for long term growth what you're saying is pretty important. Any link to a proof you're mentioning? I'd love to read some more about this. I'd like to see the correlation between consumer savings rates and bank financing rates.
ETA: Passing thought. Hasn't there also been a weak demand for credit in the last few years? I remember stories of companies sitting on all kinds of cash. Hmm, food for thought.