TOKYO, Dec 30 Japan’s Nikkei share average dropped to a three-week low in choppy trade on Friday as investors took profits from the recent gains on the last trading day of 2016, but the market managed to eke out marginal gains for the year. The Nikkei ended 0.2 percent lower at 19,114.37, the lowest closing level since Dec. 9. After trading in negative territory, the benchmark index turned positive in afternoon trade, with traders citing speculation that the Bank of Japan was buying exchange-traded funds to support the market.