According to The History of Rome, episode 126, Diocletian increased the size of the Roman imperial bureaucracy from around 15,000 people to around 30,000.
I wanted to compare the size of the bureaucracy that ran the Roman Empire to the size of the bureaucracy that runs Houston, TX. This page suggests that the city of Houston has about 68,000 employees. But far more people work for government in other capacities than work for the city. According to Table 1 of this page, the latest estimate is that 361,800 in the Houston MSA work in the government sector. And about 22 million people work in the government sector nation wide.
Please don’t leave comments saying the Roman Empire and Houston are not directly comparable. Of course they’re not. But still, a very rough comparison is interesting.
Related post: Pax Romana