A yawning growth gap has opened between city and country as Sydney's dynamic economic hubs streak ahead of the rest of the state.

Economic growth in Sydney averaged 2.2 per cent between 2012 and 2015, while regional areas of NSW contracted by 0.3 per cent in that period, research by SGS Economics and Planning has revealed.

Between 1.6 million and 2.7 million people in NSW experienced at least one year in recession between 2012 and 2015, the analysis shows.

Meanwhile, parts of Sydney have boomed. The Ryde-Macquarie Park area, a hub for high-value, knowledge-based services, grew by a runaway 5.8 per cent in 2014-15.