11/1/19: A Behavioral Experiment: Irish License Plates and Household Demand for Cars

While a relatively well known and understood fact in Ireland, this is an interesting snapshot of data for our students in Behavioral Finance and Economics course at MIIS.


In 2013, Ireland introduced a new set of car license plates that created a de facto natural experiment in behavioural economics. Prior to 2013, Irish license plates contained, as the first two digits, the year of car production (see lower two images). Since 2013, prompted by the ‘fear of the number ’13’’, the license plates contain three first digits designating the year and the half-year of the make.

Prior to 2013 change in licenses, Irish car buyers were heavily concentrated in the first two months of each year - a ‘vanity effect’ of license plates that provided additional utility to the earlier months’ car purchasers from having a vehicle with current year identifier for a longer period of time. Post-2013 changes, therefore can be expected to yield two effects:
1) The ‘vanity effect’ should be split between the first two months of 1H of the year, and the first two months of 2H of the year; and
2) Overall, ‘vanity effect’ across two segments of the year should be higher than the same for th period pre-2013 change.

As chart above illustrates, both of these factors are confirmed in the data. Irish buyers are now (post-2013) more concentrated in the January, February, July and August months than prior to 2013. In 2009-2012, average share of annual sales that fell onto these four months stood at 44.8 percent. This rose to 55.75 percent for the period starting in 2014. This difference is statistically significant at 5% percent level.

The share of annual sales that fell onto January-February remained statistically unchanged, nominally rising from 31.77 percent for 2009-2012 average to 32.56 percent since 2014. This difference is not statistically significant at even 10%. However, share of sales falling into July-August period rose from 13.04 percent in 2009-2012 to 23.19 percent since the start of 2014 This increase is statistically significantly greater than zero at 1 percent level.

Similar, qualitatively and statistically, results can be gained from looking at 2002-2008 average. Moving out to pre-2002 average, the only difference is that increases in concentration of sales in January-February period become statistically significant.

In simple terms, what is interesting about the Irish data is the fact that license plate format - in particular identification of year of the car make - strongly induces a ‘vanity effect’ in purchaser behaviour, and that this effect is sensitive to the granularity of the signal contained in the license plate format. What would be interesting at this point is to look at seasonal variation of pricing data, including that for used vehicles, controlling for hedonic characteristics of cars being sold and accounting for variable promotions and discounts applied by brokers.