The term ''bubble'' means different things to different people. American economists Karl Case and Robert Shiller define it as referring to a ''situation in which excessive public expectations of future price increases cause prices to be temporarily elevated''.

In their paper Is there a bubble in the housing market?, referring to the US, they write: ''Homebuyers think that a home that they would normally consider too expensive for them is now an acceptable purchase because they will be compensated by significant further price increases. They will not need to save as much as they otherwise might, because they expect the increased value of their home to do the saving for them. First-time homebuyers may also worry during a housing bubble that if they do not buy now, they will not be able to afford a home later.

''Furthermore, the expectation of large price increases may have a strong impact on demand if people think that home prices are very unlikely to fall, and certainly not likely to fall for long, so that there is little perceived risk associated with an investment in a home.'' Sound familiar?

Somewhere along the line our parents' generation became enamoured with debt. The very notion of debt is that it is OK to have, until it's not. Debt is not growth. Economists for the big four banks will tell us that ABS household income has increased by the same amount as the ABS house price index since 2002. Indeed it has, however this does not give us the full story of debt build-up from the 1970s. So where are we now? Well it depends on who you ask.

If you ask a young Australian, the dream of owning one's home in Sydney is dying. A survey by mortgage insurance provider Genworth in 2011 showed the average age of first-home buyers had risen to 31, up from 25 in the 1970s. Is it any coincidence Sydney's first-home buyers are getting older as the price of property rises?