A robust services sector has been the key for China's better-than-expected economic performance in the first half, despite the slowdown in the industrial sector, a sector-wise breakdown of GDP data has shown.

The tertiary industry (mainly service) expanded 8.4 percent in the first half, up from 7.9 percent in the first quarter and in comparison with the 6.1 percent growth in the secondary industry, according to the National Bureau of Statistics.

The bull run before mid-June in the equity market brought huge benefits for the financial sector. In Shanghai, added value from the sector soared by 30.1 percent over a year earlier, while the added value from the tertiary industry accounts for 67.1 percent of Shanghai's GDP. In Beijing, the finance, information and technology service industries contributed more than 70 percent to GDP growth in the first half of the year.

In Zhejiang, added value from the finance sector grew by 18.2 percent in the first half while real estate grew 13.7 percent.

Extra turnover in the stock market contributed 0.8 percentage point for China's GDP in the second quarter and 0.5 percentage point in the first quarter, Standard Chartered Bank estimated. In other words, without the surge in turnover, China's GDP would have grown by just 6.5 percent in the first quarter and fallen to 6.2 percent in the subsequent quarter.

Turnover of the stock market in the first quarter increased 169 percent over a year earlier and surged by 485 percent in the second quarter.

Discussions are already underway on whether the extraordinary capital market came at the expense of real economy, a phenomenon named "siphon effect".

"Services are more job intensive and less capital intensive. A larger role for services should support the rebalancing agenda. That said, we suspect that an unsustainable burst in financial sector output is part of the picture," said Tom Orlik, a Bloomberg economist.