Japan’s key inflation gauge has further accelerated to the fastest pace since 1981, an outcome that will continue to fuel speculation the Bank of Japan will surprise markets again with policy change down the line.

Consumer prices excluding fresh food climbed 3.7% in November from a year ago, the internal affairs ministry reported Friday. The result for the core index targeted by the BOJ matched an estimate by economists. The gain in overall inflation was a touch weaker than expected.

Higher processed food prices were the biggest driver behind the acceleration as they further outstripped the impact of higher energy costs from a year earlier. A wide range of government measures including travel subsidies helped keep price growth below 4%.