I was aware that the Behavioural Insights Team had done some business with local government in Australia last year and it seems that the collaboration is starting to pay dividends. The BIT's work on tax letters has centered around simplification and the use of social normative messages ("9 out of 10 people pay their tax..") and this intervention seems centered around those two themes also. Since the media generally inconsistently report percentages I'm not sure if the stated 5-6% and 12% improvements are really in percentage terms or if they mean percentage points. If it's the latter, those would be very large effect sizes.
Full story: http://www.canberratimes.com.au/comment/mind-games-could-pay-handsomely-20131116-2xnhp.html