the visitors' fans (although in local derbies and crosstown rivalries this may not always be the case). In some sports, such as association football, sections of the stadium will be reserved for supporters of one team or the other (to prevent fan violence) but the home team's fans will have the bulk of the seating available to them. In addition, stadium/arena light shows, sound effects, fireworks, cheerleaders, and other means to enliven the crowd will be in support of the home team. Stadium announcers in many sports will emphasize the home team's goals and lineup to excite the crowd. Ryan Boyko, a research assistant in the Department of Psychology in the Faculty of Arts and Sciences at Harvard University, studied 5,000 English Premier League games from 1992 to 2006, to discern any officiating bias and the influence of home crowds. The data was published in the Journal of Sports Sciences and suggested that for every additional 10,000 people attending, home team advantage increased by 0.1 goals. Additionally, his study found that home teams are likely to be awarded more penalty kicks, and this is more likely with inexperienced referees. Further, home players can be accustomed to peculiar environmental conditions of their home area. The city of Denver, being above sea level, has thinner air, enough so that it affects the stamina of athletes whose bodies are not used to it. Although baseball is less aerobically demanding than many other sports, high altitude affects that sport's game play in several important ways. Denver's combination of altitude and a semi-arid climate (the city averages only about 16 in/400 mm precipitation annually) allows fly balls to travel about 10% farther than at sea level, and also slightly reduces the ability of a pitcher to throw an effective breaking ball. The low humidity also causes baseballs to dry out, making it harder for pitchers to grip them and further reducing their ability to throw breaking balls. Consequently, the Colorado Rockies have a very large home advantage, with a 30% better home than away record. This anomaly has been countered with Colorado's innovative use of humidors to keep the baseballs from drying out. Denver's altitude advantage has also come into play in gridiron football; the second longest field goal in National Football League history took place in Denver, as did the longest recorded punt. The national association football team of Bolivia also enjoys the advantage