My guess is the Reserve Bank is a lot more worried about the weak 
state of the economy than it's prepared to admit in its soothing words 
and the small downgrade to its growth forecast.
 
        That's the only explanation I can think of for its decision 
to cut the official cash rate by 0.25 percentage points last week, 
despite governor Glenn Stevens' most recent "forward guidance" that "the
 most prudent course is likely to be a period of stability in interest 
rates".
 
                    
        The Reserve  could have preserved the credibility of its 
formal signalling regime by delaying such a tiny rate cut by just four 
weeks and using last week's statement to change its guidance, but such 
was its impatience that it reverted to its formerly forsworn practice of
 briefing selected journalists.
 
        The financial markets got the message - thus giving the 
Reserve the self-generated justification that it had to act because the 
market was expecting it to - but most business economists didn't. In 
their naivety, most economists regard the word of the governor as more 
reliable than media speculation.
 
            
        Despite the rate cut - and the assumption of at least one 
further cut - on Friday the Reserve shaved its forecast for real growth 
this year by 0.25 percentage points to 2.75 per cent, but left its 
forecast for next year unchanged at a midpoint of 3.5 per cent.
 
        So what was so worrying that the Reserve, having sat on its 
hands for 18 months, couldn't wait another four weeks so as to protect its 
reputation?
 
        The old story. This year has long been expected to be when 
mining investment spending falls hardest, leaving a huge hole in 
activity, to be filled by the resurgence of the non-mining economy, 
particularly ordinary business investment.
 
        The Reserve worries that business investment isn't recovering
 fast enough. So, despite having already cut the official interest rate 
from its peak of 4.75 per cent in late 2011, it decided to take off 
another click or two.
 
        It might make all the difference, but I doubt the high cost 
of borrowing is what's holding businesses back from expanding. More 
likely, they don't see any great scope for making a bigger buck, and 
they're not in any mood to try their luck.
 
        As central banks in other developed economies have 
discovered, when "animal spirits" aren't helping, you can get to a point
 where even exceptionally low rates do little to encourage borrowing and
 spending, when cutting rates to encourage growth is like "pushing on a 
string".
 
        There's one exception, however: borrowing for homes. The main
 reason the Reserve has waited so long to cut rates further is its fear 
this would do more to encourage musical chairs in the housing market - 
the buying and selling of existing homes - including yet more negative 
gearing.
 
        This doesn't do much to increase economic activity, but does 
bid up house prices and so add to the risk of a price bubble developing,
 particularly in Sydney and Melbourne.
 
        It also leads to faster growth in household debt. Saul 
Eslake, of Bank of America Merrill Lynch, notes that after stabilising 
for some years, the ratio of household debt to annual household income 
has been rising to more than  150 per cent and will now go higher.
 
        With their official interest rates down virtually to zero, 
the Americans, Europeans and Japanese have already got close to the 
limits of monetary policy. They've had to resort to "quantitative 
easing" (creating money out of thin air), but this has done a lot more 
to distort exchange rates and inflate prices in asset markets than it 
has to encourage real economic activity.
 
        At 2.25 per cent, our official rate is still well above zero 
but, even so, we're close to the point where the costs and risks of a 
rate cut threaten to exceed the benefits.
 
        The upshot of the great battle between Keynesians and 
monetarists in the 1970s was agreement that monetary policy was the most
 effective way to fight the opposing evils of inflation and 
unemployment.
 
        By the 1990s, some concluded that manipulation of interest 
rates by independent central banks had conquered the problem of keeping 
economies on an even keel. Yeah, sure.
 
        We discovered a fatal weakness in the new macro management: 
monetary policy was great at controlling ordinary inflation, but when 
used to stimulate weak demand it was prone to encouraging excessive 
borrowing and asset-price bubbles which, when inevitably they burst, 
caused deep and protracted "balance-sheet" recessions.
 
        From our perspective, the answer to our present problem isn't
 more risky rate cuts, it's greatly increased federal spending on 
infrastructure to fill the hole created by the fall in mining 
investment.