I don't think you have actual numbers and stats to speculate this unfortunately. But a few things to consider; the west has continued to pillage Africa long after the abolishment of 'colonialism', an example, go look at those mine dumps outside of Joburg, it's very favourable for the west to mine here as there is very little profit spent on dealing with this radioactive, toxic mess.
Another thing to consider is 'opportunity loss'. You might be able to figure out the 'to-the-cent' theft from both the Nats & the ANC, however, the actual costs are not just that. It's the damage to state-owned assets and business' (NB - the ANC is the ruling party, NOT the state, which is often forgotten - that failed post office is OUR post office, not theirs), the damage to future economies (for instance the opportunity cost loss from no digital migration), the loss of investment, and the loss of our brilliant minds (this last one is the biggest cost/loss, and NBNB this is people of ALL races. I know of many many highly skilled black people who've left for greener pastures).
So while yes, you can make a blanket assumption, it has no basis in actual economics, but if you want the easiest indicator of this, look no further than the ZARand in relation to other currencies. It doesn't take much to make the correct assumption from there.