While most US media claims China (PRC) has the world's second largest economy, that is only true as measured in nominal terms. Measured in real PPP terms, Chinese GDP surpassed that of the US in 2015 and contnes to move further ahead of it (and is likely to pass it in nominal terms very soon), despite gradual deceleration of the Chinese GDP growth rate. Furthermore, PRC seems to be taking global leadership in crucial 5G technology. In the last 70 years the PRC has gone from a poor nation wracked by regular famines to a solidly middle class nation with vastly reduced poverty and no famines for many decades (although there was an especially severe one in the late 1950s that killed millions in the early part of the regime).
I would like to put this anniversary into a broader historical perspective, in particular from a traditional Chinese view. That is that while there have been exceptional periods, most of Chinese history has been driven by dynasty cycles, with the average life of a dynasty being about 300 years, as with the Tang, Song, Yuan, Ming, ans Qing (the Han lasted 400 years, some others for much shorter periods). The classic pattern has been for the first century to be dynamic, with proper Mandarin civil service exams associated with a competent bureaucracy and effective management of the agro-hydraulic infrastructure, with a growing economy. The second century involves a flattening out and slowing of growth. In the third century corruption of the exams rises as does general corruption and stagnation as the incompetent bureaucracy mismanages the infrastructure and the broader economy, with all this leading to the Malthusian disasters of war, famine, and pestilence, and the eventual collapse of the dynasty.
In this perspective the Communists are a new dynasty, now getting into the later stage of their first century, although some would say the new dynasty started with the end of the Qing a century ago. Of course technically that first post-Qing regime/dynasty survives in Taiwan, which has done far better economically than has the PRC. In any case, the rapid growth PRC has seen since the Dengist reforms 40 years ago have been that initial dynamic phase of an early dynastic period. What we are seeing now with the current slowdown is the move towards that second century regularization, which is marked by Xi harking back to the origin of the dynasty with Mao. This is all the more so given the challenge posed by the ongoing uprising in Hong Kong.
Beside Hong Kong and apparently Taiwan, the expansion of Chinese power and influence across much of the world, especially through the Belt and Roadd initiative, may be running into limits. Reports from various nations, most recently Pakistan, is that many are becoming unhappy with the conditions associated with this initiative and are pulling back or resisting deeper involvement. We shall continue to see Chinese growth and expansion of global influence, but this anniversary marks a point where the nature of this is changing to a more constrained path. This will prove a serious challenge to the Chinese leadership, both while Xi is in power, but even more for his successors.