The Organisation for Economic Co-operation and Development (OECD) just released a foreign bribery report that analyzes more than 400 cases worldwide involving companies or individuals from the 41 signatory countries to the OECD Anti-Bribery Convention who were involved in bribing foreign public officials.

The cases took place between February 1999, when the Convention came into force, and June 2014.

The OECD found that “most international bribes are paid by large companies, usually with the knowledge of senior management.”

Bribes in the analyzed cases equalled 10.9% of the total transaction value on average, and 34.5% of the profits — equal to $13.8 million per bribe.

But because bribes are so hard to detect, “this is without doubt the mere tip of the iceberg,” the OECD said.

The report found that bribes are generally paid to win contracts from state-owned or controlled companies in advanced economies, rather than in the developing world, and most bribe payers and takers are from wealthy countries.

Almost two-thirds of the cases occurred in just four sectors: extractive (19%), construction (15%), transportation and storage (15%), and information and communication (10%).

Bribes were promised, offered or given most frequently to employees of state-owned enterprises (27%), followed by customs officials (11%), health officials (7%), and defense officials (6%).

Heads of state and ministers were bribed in 5% of the cases but received 11% of the total bribes.

In most cases, bribes were paid to obtain public procurement contracts (57%), followed by clearance of customs procedures (12%). Six percent of the bribes were to gain preferential tax treatment.

OECD Secretary-General Angel Gurría said: “The prevention of business crime should be at the center of corporate governance. At the same time, public procurement needs to become synonymous with integrity, transparency and accountability.”

In 41% of the cases, management-level employees paid or authorized the bribe, and the company CEO was involved in 12% of the cases.

Intermediaries — agents, distributors, brokers, subsidiaries, offshore shell companies — were involved in 3 out of 4 foreign bribery cases.