Five years ago, one forecast had China amassing a submarine force of as many as 180 boats by the mid-2020s – enabling it to outnumber the U.S. Pacific Fleet's submarine force by five to one according to a widely cited estimate published by John Tkacik. Developing such a force in this time frame required China to add six subs a year to their fleet, above replacement level – and virtually the whole current fleet would have to be replaced, given that the bulk of it is comprised by obsolete, aged Romeo, Ming and Han-class boats sure to be past their useful life by then.
In short, China would have had to launch eight boats every year for almost two decades to reach a force size of 180 subs. Such a rate of peacetime production seemed very unlikely to me. On the contrary, China's modernization of its modern forces has tended to produce smaller (though more up-to-date) forces.
A new analysis by David Axe in The Diplomat indicates that this is exactly what has happened. In the 2007-2010 period, China added a mere six subs to its fleet, a small fraction of the frantic rate of production needed to realize the higher estimates. As a result, China has some sixty submarines in 2011, its size remaining well below the aggressive estimates offered by analysts hyping the "China" threat (though modern Song and Kilo-class boats have replaced many of the older vessels in that time). It also seems likely that this force will shrink in the coming years, with Russia less willing to sell additional submarines (projections based on the Chinese Kilo purchase, in fact, seems to have contributed significantly to the overestimates of China's sub force increases).
Moreover, it is worth noting that boat-counting has its limits. There are significant differences between the relative handful of nuclear boats China seems likely to possess, and the diesel boats that seem likely to continue to comprise much of the country's fleet. The most important are submerged range and speed. The Kilo-class sub can sail six thousand miles while snorkeling at a speed of seven knots, while fully submerged, it can only do four hundred miles while crawling along at three knots (in comparison with a nuclear-powered Los Angeles-class submarine, which can sustain twenty knots while submerged, over a range limited only by the endurance of the crew).The upshot is that in today's threat environment, conventional submarines can be very effective in a coastal defense role, but are rather less suited to the kind of long-range operations undertaken by "blue-water" naval powers than the nuclear-powered vessels that make up the whole of the U.S. Navy's force. Additionally, as Axe notes, a straight comparison between the U.S. and China is simplistic given – as so many continually forget – China is itself surrounded by other countries with considerable naval establishments, and submarine forces, of their own, including Russia, Japan, India and South Korea.
The result, as Axe notes, is that "China isn’t building a world-class, globally-deploying submarine force. It’s building a mostly defensive, regional undersea force – and a smaller one than once predicted."
Keeping the Hype in Check III: China as Global Military Power
Keeping the Hype in Check II: The ASBM
Keeping the Hype in Check I: The Chengdu J-20