Despite the correlation of the decline of corporal punishment (acceptability) with societal/cultural performance? Prison population as metric or proxy, for example. Or income disparity.
Absolutely.
Prison population is an abysmal "metric or proxy" for societal performance – especially when you watch crime rates
decrease while prison population continues to increase apace. (But that's what happens when you imprison people for non-crimes.)
Income disparity? The connection to corporal punishment is beyond tenuous. Inflation, income tax (not to mention sales tax, gas tax, etc...), a regulatory environment which favors and incentives large over small businesses (and which tends to result in reduced wages for those farther down the employment ladder) are far more direct and plausible causes.
Finally, correlation does not imply causation. Worse, social statistics are nearly universally worthless.
Anecdotes aren't worth much more, but I can share my experience: I was spanked occasionally as a child. I remember being spanked, but I don't remember a single misdeed attached to any of these instances of "remediation". On the other hand, I can recall specific memories of my parents showing me good behavior by example, and explaining morality to me in a simple, effective (i.e. not dependent on religion or superstition) manner.
From this analysis I've concluded that corporal punishment is next to useless. It may result in an immediate and temporary cessation of annoying behavior, but it's virtually impossible to teach a person through violence.
I suspect this strongly enough that I'm quite comfortable stating that any person who reacts in the intended fashion to corporal punishment is born to be subservient, and that subservience is therefore the only behavior corporal punishment can actually "teach" (reinforce, really). So, I might correlate the use of corporal punishment with the rise of statism in the 20th century.
Of course absentee and apathetic parents are likely to raise their children poorly. But it's contrary to reason (and my experience) to assume that corporal punishment is the sine non qua of engaged, effective parenting.