Since The Bell Curve was published, it has become clear that almost everything about it was inexcusably  suspect data, mistakes in statistical procedures that would have flunked a sophomore (Murray--Herrnstein is deceased--clearly does not understand what a correlation coefficient means), deliberate suppression of contrary evidence, you name it.
The Bell Curve is based on faulty data and unethical work.
The Bell Curve's findings have been proven absolutely correct.