In the summer of 2001, three-quarters of the 170 million Brazilians were told that they must immediately cut consumption by 20 percent or face rolling blackouts and unscheduled power interruptions. The measures were needed because of an exceptional drought (Brazil obtains more than 90 percent of its electricity from dams and has not invested extensively in alternatives). Outdoor street lighting has been cut by one-third, and nearly every nighttime activity in major cities was affected. Few ordinary Brazilians had any inkling of the seriousness of the crisis. Officials warned that it may become necessary to order the nation to adopt a four-day work week, giving employees Mondays off until the end of the year.