Why did South Africa have lower crime rates under Apartheid?

I've heard the crime rates in South Africa were much lower under the Apartheid government. I don't understand that. I would think that people would break the law more often while oppressed rather than while free...
Update: @Thunee Man Naidoo - I wasn't being racist at all; I was simply asking a question because I didn't understand something. None of the other answers have been racist at all...

@Everybody else - Thanks for your answers!
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