Football is the most popular spectator sport in the United States, and with annual revenues topping $8 billion the National Football League is the country's wealthiest professional sports organization. But the league was on the defensive during the 2009–2010 season because of a jarring debate over its alleged indifference toward player safety and health. Medical research now indicates a connection between concussions that players routinely suffer during games and long-term brain disease, including dementia. Under pressure from the NFL Players Association, news media and Congress, the NFL is belatedly acknowledging a possible link and trying to minimize the risk to players by, among other changes, limiting a player's return to the game after a concussion. Despite football's popularity, the NFL is also facing economic difficulties. Attendance sagged during the 2009–2010 season, the future of lucrative TV contracts is cloudy and the league and the players' union start out far apart as negotiations begin for a new collective-bargaining agreement.