Japan’s inflation has quickened to its fastest pace in over three decades excluding tax-hike distortions, creating headaches for the Bank of Japan this week as it seeks to explain why it needs to continue with monetary stimulus when inflation is far above its 2% goal.

Consumer prices excluding fresh food rose 2.8% in August from a year ago, the internal affairs ministry reported Tuesday. Analysts had forecast a 2.7% gain. It was the strongest reading since 1991, barring the effect of sales tax increases.

Rising energy and processed food costs continued to account for most of the year-on-year increase, while higher electricity prices and a smaller drag from mobile phone fees contributed to the acceleration.