Corrupt practices whose sole outcome is to ACCELERATE decision making, the provision of goods and services or the divulging of information. None of the outcomes or the utility functions are altered. Only the speed of the economic dynamics is altered. This kind of corruption is actually economically BENEFICIAL. It is a limited transfer of wealth (or tax) which increases efficiency. This is not to say that bureaucracies and venal officialdoms, over-regulation and intrusive political involvement in the workings of the marketplace are good (efficient) things.
They are not. But if the choice is between a slow, obstructive and passive-aggressive civil service and a more forthcoming and accommodating one (the result of bribery) - the latter is preferable.
Acceleration fees are collected mostly by mid-ranking bureaucrats and middle rung decision makers in both the political echelons and the civil service.