Which do you expect to witness more often in your lifetime, Powerball/Lotto jackpot winners or one-in-1000 year floods?

This well-written piece in The Guardian explains the issue with translating a probability of 0.001 (i.e. 0.1%) to a “one-in-1000” year flood. There is a temptation with this wording to think that we shouldn’t experience another flood of this significance in our lifetimes and therefore not to plan for it. 

Do you know the probability of winning Powerball in Australia, which is played every Thursday night? It is currently 1 in 134.5 million (0.00000074%).* 

Someone won the top prize on August 16, 2018, taking home a whopping $100 million. But are we surprised that Powerball was won again in January 2019? Absolutely not. 

We know it is rare to win this game, but the slim chance is always there. We recognise that after the win in August 2018 we do not need to wait another 134.5 million weeks (give or take) before another person wins. Otherwise no one would buy tickets! 

There was a 0.1%** chance of the severe level of flooding we are currently experiencing along the East Coast of Australia, so we will see more in our lifetimes. For more on the probabilities around weather, check out my post on understanding weather forecasts.

*I don’t gamble as I know the stats involved, but I’m using Powerball as an example. Thank you Wikipedia for the details)

** Chances/probabilities of an extreme flood event can be updated retrospectively as more data becomes available over time.