The benchmark Nikkei stock index finished the year down 9.4 percent on Friday, its first yearly fall in four years, as the result of aggressive monetary tightening by central banks offset the impact of solid corporate earnings with the yen’s historic fall, Kyodo reported. In the final trading day of the year, the 225-issue Nikkei Stock Average ended up 0.83 points, or 0.00 percent, from Thursday at 26,094.50. The broader Topix index finished 3.56 points, or 0.19 percent, lower at 1,891.71. On the top-tier Prime Market, gainers were led by marine transportation, bank and retail issues. Mining, oil and coal product, and food shares were among the worst performers. The yen firmed to the lower 132 level against the U.S. dollar in Tokyo amid a decline in long-term U.S. Treasury yields. The Japanese currency had weakened to near the 152 level in October, losing about 38 yen in value since its strongest level in January, its biggest yearly drop in 40 years.