2.31bn RFID tags were sold in 2010

"In retail, RFID is seeing rapid growth for apparel tagging. RFID in the form of tickets used for transit will demand 450 million tags in 2011. The tagging of animals (such as pigs, sheep and pets) is now substantial as it becomes a legal requirement in many more territories, with 243 million tags being used for this sector in 2011. This is happening in regions such as China and Australasia. In total, 2.88 billion tags will be sold in 2011 versus 2.31 billion in 2010. Most of that growth is from passive UHF RFID labels."

Source:  IDTechEx, August 2011