This paper explores the changes in consumers' loyalty towards wine after the launch of the new common market organization (CMO) (European Council Regulation (EC) No. 479/2008) in 2008. The analysis of wine purchases in the AC Nielsen Consumer Panel in 2009 and 2010 was compared to analogous work conducted in 2003–2005 and 2006–2008. Loyalty towards wine attributes— price, quality designation and packaging format—was measured using standard brand performance measures together with a newer metric, the polarization index, which has not been used before to highlight or explain the factors behind shifts in loyalty. The analysis revealed that post‐CMO reform increases in consumer loyalty towards the following: (i) standard 0.75‐L wine bottles; (ii) quality‐classified, protected designation of origin wines; and (iii) higher‐price‐point wines. The paper elaborates these findings, explaining how changes in consumers' loyalty patterns can be used to quantify the success of recent policy changes, which can be tracked in a reasonably short time frame thanks to the polarization index. Copyright © 2014 John Wiley & Sons, Ltd.