Guinness (pronounced IPA: /'g?n?s/) is a dry stout that originated in Arthur Guinness's St. James's Gate Brewery in Dublin, Ireland. The beer is based upon the porter style that originated in London in the early 1700s. It is one of the most successful beer brands in the world, being exported worldwide. The distinctive feature in the flavour is the roasted barley which remains unfermented. For many years a portion of the beer was aged to give a sharp lactic flavour, but Guinness has refused to confirm if this still occurs. The thick creamy head is the result of the beer being forced—under high pressure—through five tiny holes in a metal disc in the tap. It is extremely popular with the Irish and is the best-selling alcoholic drink of all time in Ireland, where Guinness & Co. makes almost €2 billion annually.