China's economy grew 6.9 per cent year on year in 2015, the slowest annual expansion in a quarter of a century, but it is still in line with the official target, according to data from the National Bureau of Statistics (NBS) on Tuesday., the lowest quarterly rate since the global financial crisis, the data showed.. The country's gross domestic product (GDP) reached 67.67 trillion yuan (about $10.3 trillion) in 2015, with the service sector accounting for 50.5 per cent, the first time the ratio exceeded 50 per cent, according to the NBS.However, the country faces a daunting task in deepening reforms on all fronts and needs to step up supply-side structural reforms, he said. Major economic indicators softened in 2015, with industrial output growth slowing to 6.1 per cent year on year from 8.3 per cent in 2014, NBS figures showed.Urban fixed-asset investment continued to cool, expanding 10 per cent year on year, compared with 15.7 per cent in 2014. Retail sales rose 10.7 per cent, down from 12 per cent registered in 2014. Foreign trade ended 2015 with its first annual contraction in six years. Sagging global trade, rising financial risks and changing domestic market conditions were among the factors affecting the economy, NBS Chief Wang told reporters on Tuesday.He also pointed to an ailing property sector and stock market fluctuations but said their impact on the economy was either limited or yet to be evaluated. Wang dismissed worries about China's government debts, noting that they accounted for less than 40 per cent of the country's GDP, well below the internationally accepted alert line of 60 per cent.