It is two of the smallest categories in the spirits industry that is driving the most growth: Irish whiskey and prepared cocktails. Irish sales grew 23% and volumes gained 21.5%, with average prices up 26 cents a 750ml bottle to $22.35 in the 52-weeks to September 17 based on Nielsen food, drug and liquor store scans. Prepared cocktails, meanwhile, grew sales by 18.3% in the 52-weeks and volumes rose 15.2%. Average prices were up 18 cents to $6.95 a bottle. SkinnyGirl and Daily's, both of which have prompted a wave of new wine-based and spirits-based prepared cocktails with regular and low calorie offerings, are driving much of that growth.