According to the screw cap producer Guala 15% of all the world’s wines are now sealed with screw cap, thanks to an increase of 25% for the metallic closure in 2008. According to Nomacorc, who produces plastic corks, the market for screw caps is 2.5 billion, dwarfed by the plastic cork market of 4 billion units. Amorim, who makes natural cork, estimates the screw cap market to be somewhat smaller than that. Decanter.com
