Launch rate and commissioning rate for 052D have been at around 2.5 per year. But this is just taking the totals and dividing by 4 in the case of commissioning, and 6 in the case of launching. I doesn't mean the construction follows such a regular pace, and keel laying events, launching, and commissioning can vary from one to 4 or even more, in the case of 2018.
Aside from this, the longer term rates don't have to stay the same either, and we may be witnessing a stepping up of the pace. If we accept the rumor that the carrier program has been accelerated (and facts seem to support this), shouldn't it be clear that construction of escorts would be accelerated as well? In fact, this seems to be happening in all areas of the navy, not just aircraft carriers and their escorts.
Launch rate is now up to 3-4 destroyers per year. And all those ships will be commissioned at some point in time.
In terms of China speeding up naval construction, China has lots of spare shipbuilding capacity but wage increases are still fairly fast.
So there's no better time to build lots of ships, which is labour intensive.
Plus if you look at the political situation, a majority of both Democrat and Republican politicians now agree that China is the main strategic competitor to the USA.
I always thought this outcome was inevitable, because the USA has gotten used to being the sole unchallenged superpower in the world. But that is no longer the case as:
1. China now has an economy larger than the US in actual output of goods and services, as measured by Purchasing Power Parity.
2. China spends a modest 2% of GDP on the military. That is a lot lower than the USA, which habitually spends 3-4% of GDP.
3. The National Science Foundation reported to Congress that China is expected to outspend the USA in R&D in 2019. It means China will likely become a high-tech country. And a high-tech country is likely to escape the middle income trap, when countries don't move up the economic value chain.
So it shouldn't be a surprise that China has decided to increase the pace of naval shipbuilding.
My estimate is that Chinese economy is already big enough to sustain 4 destroyers per year indefinitely.