Meanwhile, Britons can save more than £5,000 in 100 days with the envelope challenge.
To get started, people will need to label 100 envelopes with the numbers 1 to 100.
For 25 consecutive weeks, twice a week, people will need to draw out two envelopes at random and save the amount written down.
For example, if someone picks the envelope with the number 99 on it, they need to put £99 inside it but if they pick the envelope with five on it, they will only need to save £5.