Sins Of A Solar Empire publisher Stardock has estimated that Valve's Steam holds a 70 per cent share of the digital distribution market.

The company believes that its Impuse service is the second largest player in the marketplace, it said in its annual customer report (pdf), which was spotted by Gamasutra.

"Our estimation is that Steam - as the current market leader - enjoys approximately 70 per cent of the overall digital distribution market with Impulse at ten per cent and all others combined at 20 per cent in terms of actual dollars generated per month," said Stardock boss Brad Wardell.

Steam and Impulse, which launched in 2003 and 2008 respectively, “both have the advantage of exclusive content (Left 4 Dead, Half-Life, Sins Of A Solar Empire, Demigod, etc.)", he noted. Other players in the field include the likes of Direct2Drive and GamersGate.

Wardell also said that he expects digital distribution to have generated around a quarter of the revenues "for a typical PC game publisher on a new title" this calendar year.