Those 15% is actually if they know someone who has committed academic misconduct not fraud (although there is an overlap it's not the same), and it is across all levels (I.e. from PI to PhD student). So this will very likely overestimate fraud, as we would be double counting (I.e. Multiple reporters will know the same person). Imporantly the paper also says if people reported the misconduct it had consequences in the majority of cases.

And just again for comparison >30% of elite athlete say that they know someone who doped.