The idea of corruption is quiet complex. There are even economists that argue, that slight corruption leads to a more efficient economy, due to minimizing beaucracy.

Nevertheless, corruption can lead to people loosing faith into their government and therefore its inability to fulfill its role in society.

Therefore, this index measures ‘perceived corruption’. If you are interested in a more in depth explanation, I would suggest watching economics explained video to this topic: youtu.be/s4C1xiyGaGs?si=rTkOZAWbGKXzjLok

But a single ‘this index is bullshit meaningless’ is not paying justice to the complexity of this topic.