The installed base of “big brand” tablets – from vendors such as Apple and Samsung – will pass 285 million units at the end of 2013, according to ABI Research.

In the US, which has been “the largest single tablet market since inception”, the total is more than 70 million, or about one for every four people.

Jeff Orr, senior practice director for the company, said: “The initial iPad shipments are aging out with the first wave of replacement tablets expected over the next six months. We believe about 51 per cent of the tablet installed base is coming from iOS and 40 per cent Android when all is said and done in 2013.”

The company also noted that Samsung “continues to make gains in the Android tablet segment”, with 20 per cent growth in the third quarter of 2013.

The South Korean giant has increased its marketing spend as it promotes several tablet sub-brands, “and looks to receive some halo effect from the success of its Galaxy S4 smartphone and the Galaxy Gear companion smart watch device”.

Apple has also “shored up its two-year ASP haemorrhaging” by increasing its iPad value “nearly 1 per cent to $439”.

Unit shipments in Q3 were down 4 per cent from the prior sequential period and revenue down about 3 per cent, ahead of the launch of the iPad Air and second-generation iPad Mini.