Japan is a parliamentary constitutional monarchy, located in the Eastern Asia. Legislative and executive powers are vested in the Diet (parliament), which consists of the House of Councillors (the upper house) and the more powerful House of Representatives (the lower house). Japan is the 5th largest economy in the world (by GDP PPP) and is among the world's largest and most technologically advanced producers of motor vehicles, electronic equipment and machine tools. Around 49% of Japan’s merchandise exports are directed to just three markets (United States, China and European Union). Total external trade volume is only 18% of GDP, which is a rather low figure. The central bank, Bank of Japan (BoJ), pursues an inflation-targeting approach to monetary policy and maintains a free floating exchange rate regime. Ageing population, huge public debt and large public deficit as well as high dependency on energy imports are usually named among key weaknesses of the Japanese economy.