What is the typical kickback percentage?

Factual Questions
1

In the US or abroad, when a corrupt pol awards a contract to a briber, what is the typical kickback percentage?

There is some US data. A couple of years ago Duke Cunningham (R) of Southern California was given a 10 year sentence for accepting bribes. His “Bribe Memo” had a menu of projects and required bribes, I recalculate the figures here:



Government Contract                     Bribe             Kickback Percentage
16 million                             $140,000                     0.875%
20 million                              340,000                     1.7%
25 million                              440,000                     1.76%

Are those percentages typical? Admittedly, Duke actually confessed to accepting $2.4 million in bribes, so those figures might not be representative.

How do Cunningham’s percentages compare with those on, say, corrupt city contracts in the US or in other examples of malfeasance, historical or otherwise?

2

Googling further, I found a figure from the early 20th century, connected with the construction of the Panama Canal. Allegedly, some governmental contracts were so valuable as to permit a kickback of 35%. Cite: Panama Canal Graft, a 6 paragraph column from the NYT of Oct 9, 1908.
Today, I understand that some third worlders are struck by how cheaply US officials can be bought, though this is in the context of legal campaign contributions.

Sales of military hardware have been known to enrich certain foreign governmental officials – but what’s the typical percentage?