The latest quarterly smartphone sales data from Gartner is out today, and it tells a very familiar story. BlackBerry keeps shrinking, Microsoft is stagnating, and Google and Apple are tightening their already dominant grip over the entire market.

Out of 329 million recorded phone sales over the past three months, 319 million ran either Google's Android operating system or Apple's iOS alternative. That represents 96.8 percent of the market, matching the first quarter of this year for the highest proportion controlled by the two biggest platforms. The present smartphone market is, for all intents and purposes, just these two American giants duking it out.

Intriguingly, though, Gartner suggests that this constantly booming industry might finally be reaching maturity, as even the growth-spurring Chinese market "has reached saturation — its phone market is essentially driven by replacement." That's led to the slowest growth in global smartphone sales (13.5 percent) since 2013, and Gartner suggests that attracting customers at the two extremes — premium smartphones for luxury buyers and affordable 4G handsets at the low end — will be "key for vendors to attract upgrades and to maintain or grow their market share in China." Running the right software will also surely help, which if you're not selling iPhones, is going to be very definitely Android. The duopoly that these two companies have established is looking more unconquerable than ever.