>>508750786
To be more precise, roughly half of all free people in Rome were living off the bread dole. With roughly a million people, around 300,000 were slaves. The rest were free, although not all were citizens. Of those citizens, about a quarter million men were registered for the welfare, which they used to feed their families.

Given that only male citizens were eligible, you could divide the city's non-slave population by half and easily see that most people were subsisting off government welfare.