Square eyes today were a consequence of some time wrestling with numbers on the Southern Oscillation Index. So here is a preliminary graph on the effort subsequent to a more comprehensive post:
The red line here is an historical six year moving average, and the timeframe here is from 1860 until now. The volatile black line is a moving annual average.
This is no doubt metereologically unsound methodology but was selected because six years is the same timeframe the insurers and Guvmint Actary have used to validate historical underpricing in the last six years!
As can be seen the 'historically underpriced' period of the last six years is one of only four similar extreme La Nina events in the 150 years on the record.
Selective data is usually to be expected but how disappointing to see it unprofessionally supported by the Australian Government Actuary in a formal report?