Here's why you should take budget forecasts with a grain of salt

Budget forecasts are dramatically wrong year after year.

The budget papers once predicted a $5 billion surplus for the 2013-14 financial year. The final result was a $49 billion deficit, according to the budget Treasurer Joe Hockey handed down last week.

Budget forecasting error in Australia's federal budget

But worse than that, they're out of date in no time at all—it's a real wonder governments keep calling attention to them.

Read my full analysis with more pretty graphs at ABC News.