The Nikkei stock index fell for the fourth consecutive day Friday to end at a fresh three-week low, as a stronger yen pressured exporters and a sense of wariness prevailed before U.S. jobs data due out later in the day. The 225-issue Nikkei Stock Average ended down 265.62 points, or 0.72 percent, from Thursday at 36,391.47, its lowest level since Aug. 13. The broader Topix index finished 23.34 points, or 0.89 percent, lower at 2,597.42. On the top-tier Prime Market, decliners were led by machinery, iron and steel, and electric appliance issues. The U.S. dollar fell to a one-month low in the lo…