Well I wouldn't rely solely on the number of cranes , it does give you an indication of economic activity .
Particularly if they are not just residential high rises ( speculation ) .
For banks to lend money for this type of activity suggests there is a bit of confidence that the economy is robust . No doubt spurred on by cheap money but that is part of the cycle after all .
I assume everyone was expecting a bust after the GFC and mining boom ( I know I was ) but the longer it goes on , the less likely it appears to be the case .
Employment numbers are relatively stable , mining continues , lng investment has a couple of years to run , stockmarket up , the US is picking up etc etc .
Crane numbers i.e activity , is just one of a number of indicators that help you paint a picture of the state of the economy .