By 2010, raves were becoming the equivalent of large-scale rock music festivals, but many times even bigger and more profitable. The Electric Daisy Carnival in Las Vegas drew more than 300,000 fans over three days in the summer of 2012, making it the largest EDM music festival in North America. Ultra Music Festival in Miami drew 150,000 fans over three days in 2012 while other raves like Electric Zoo in New York, Beyond Wonderland in LA, Movement in Detroit, Electric Forest in Michigan, Spring Awakening in Chicago, and dozens more now attract hundreds of thousands of "ravers" every year. These new EDM-based rave events (now simply referred generically to as "music festivals") sell out. Festival attendance at the Electric Daisy Carnival (EDC) increased by 39.1%, or 90,000 attendees from 2011 to 2012. In 2013, EDC had attendance of approximately 345,000 people, a record for the festival. The average ticket for EDC cost over $300 and the event contributed $278 million to the Clark County economy in 2013. This festival takes place at a 1,000-acre complex featuring a half dozen custom built stages, enormous interactive art installations, and hundreds of EDM artists. Insomniac, a US EDM event promoter, holds yearly EDC and other EDM events.
Common sails consist of a lattice framework on which a sailcloth is spread. The miller can adjust the amount of cloth spread according to the amount of wind available and power needed. In medieval mills, the sailcloth was wound in and out of a ladder type arrangement of sails. Postmedieval mill sails had a lattice framework over which the sailcloth was spread, while in colder climates, the cloth was replaced by wooden slats, which were easier to handle in freezing conditions. The jib sail is commonly found in Mediterranean countries, and consists of a simple triangle of cloth wound round a spar.
In all cases, the mill needs to be stopped to adjust the sails. Inventions in Great Britain in the late eighteenth and nineteenth centuries led to sails that automatically adjust to the wind speed without the need for the miller to intervene, culminating in patent sails invented by William Cubitt in 1807. In these sails, the cloth is replaced by a mechanism of connected shutters.
In France, Pierre-Thophile Berton invented a system consisting of longitudinal wooden slats connected by a mechanism that lets the miller open them while the mill is turning. In the twentieth century, increased knowledge of aerodynamics from the development of the airplane led to further improvements in efficiency by German engineer Bilau and several Dutch millwrights. The majority of windmills have four sails. Multiple-sailed mills, with five, six or eight sails, were built in Great Britain (especially in and around the counties of Lincolnshire and Yorkshire), Germany, and less commonly elsewhere. Earlier multiple-sailed mills are found in Spain, Portugal, Greece, parts of Romania, Bulgaria, and Russia. A mill with an even number of sails has the advantage of being able to run with a damaged sail and the one opposite removed without resulting in an unbalanced mill.
In the Netherlands the stationary position of the sails, i.e. when the mill is not working, has long been used to give signals. A slight tilt of the sails before the main building signals joy, while a tilt after the building signals mourning. Across the Netherlands, windmills were placed in mourning position in honor of the Dutch victims of the 2014 Malaysian Airlines Flight 17 shootdown.