In 2008, the number of sales started at approximately 40%. The number rose slowly to 55% by 2010 and then fell sharply to 20% in 2011. At this point the number of sales maintained the same level until 2012 before climbed gradually to 30% by 2013, in 2014 rose rapidly to 80% did not change to 2015. In 2016 fell swiftly to 15%