"the transaction cost theory defines and differentiates alternative institutional arrangements on contract-theoretical basis." ³⁷
Williamson differentiates three forms from contractual relations - classical, neoclassical and relational - those the completion of transactions in each case over the market, over long-term contracts and with respect to organizations corresponds ³⁸ .
Their characteristics are four important measured variables on the efficiency of the completion and organization of transactions: The incentive intensity, the control mechanisms, the adaptability as well as the costs of the establishment and use of the institutional arrangement. ³⁹
Classical contractual relations are characterised by short duration, by the clear definition of the agreed upon achievements and returns and the transaction conditions, as well as by itself a personal interaction of the contracting parties limiting to the discrete act of the transaction. ⁴⁰
Possible conflicts, which develop regarding the exchange relationship and their consequences, usually develop to a case for the courts. Classical contractual relations mark the institutional form of the completion of transactions by the market exchange between autonomous transaction partners. ⁴¹
"achievements and returns are directly and closely coupled, as well as in a high measure monetary assessably. Since each increase of the net use of the transaction flows to the transaction partners directly, each transaction partner possesses a strong interest to use its resources as efficiently as possible.
This strong interest is still increased by the competition, which the transaction partners Transaction (partner) alternative with classical contractual relations due to the small specificity of the goods or achievements and due to the relatively simple comparability of the advantage more differently are often suspended. ⁴² "
The control mechanisms are very economical thereby also, because due to the convincing threat with legal sanctions or the withdrawal of orders for exclusion often a strong incentive exists to fulfill the contracts. ⁴³
Beyond that the classical contract offers a high and economical adaptability to changed conditions, like the change of the demand, the offer or the factor price relations.
It makes autonomous adaptability possible, i.e. each transaction partner knows its allocation decision at short notice and independently, without having to co-ordinate it with others, to which changed conditions adapt. ⁴⁴
Thus cause both the agreement and the monitoring and penetration of the fulfillment of a contract - by the precise determination of the subject of a classical contract - a small expenditure.
Relational contractual relations are characterized by the establishment of a very long-term exchange relationship between the transaction partners and by openness in the ex ante definition of achievements and returns. Conflicts are decided internally on the hierarchy and solved without engagement of the courts. ⁴⁵
On relational contracts the institutional form of the completion of transactions in organizations is based. ⁴⁶
Compared with classical exchange relations the internally working incentives are here pronounced to efficient resources employment more weakly, since achievements and returns are often due to measuring and addition problems not direct and closely coupled.
Also the missing direct competition prevents that the input factors are remunerated in accordance with their border productivity . Can - by internal sliding average price systems and other bureaucratic control and incentive systems - which incentive effects of the market internally simulated and which are compensated existing incentive deficits, but the effectiveness of these measures impaired by the measuring problem. Beyond that costs of the establishment and use result. ⁴⁷
"a further implication of the problems of the power measurement consists of the fact that the persons employed can try to carry a smaller out than the agreed upon (and remunerated) contribution or to exploit other input factors over fee for the own advantage. In order to limit this possibility of opportunistic behavior, in organizations (in addition, in some hybrid institutional arrangements) specific bureaucratic control and control systems are institutionalized, those likewise to an increase of the cost level contribute." ⁴⁸
However the organization-internal achievement production possesses advantages, e.g. in view to the so-called bilateral adaptability. ⁴⁹
With ease factor combinations can be co-ordinated earmarked for special use with the respective requirements and adapted to changed conditions.
"a further advantage exists in the better information about the combination ability and achievement of different input factors.
Because over internal resources better information exists as over external and because information can be procured internally besides more simply and more economically (Cheung 1983), is it possible to combine resources organization-internally in more productive way than with marktlich obtained processes. Beyond that the better information makes a more efficient protection possible from opportunistischem behavior." ⁵⁰
For these advantages however bureaucratic costs arise and general costs of the establishment and use of the contractual relation. ⁵¹
Neoclassical contractual relations are the basis such transactions, which are carried out in hybrid institutional forms between transaction partners, whereby they defined measured variables regarding all four of Williamson on the efficiency of the completion and organization of transactions a central position between market and organization take. ⁵¹
Thus here, in contrast to classical contracts, not all conditions, which affect the costs and use of the transaction, of the transaction partners are completely anticipated and precisely fixed.
"neoclassical contractual relations are therefore often by adjustment and safeguards as well as institutionalizing conflict regulation mechanisms under private law characterized (...) the transaction partners try, at least first, to solve conflicts over arbitral tribunals instead of them to the courts to refer (one-hurry 1978; Williamson 1991)." ⁵³
In summary the following table results in view to the transaction characteristics of the three fundamental alternative institutional arrangements.

Tab. 3: Transaction characteristics of the three institutional arrangements. ⁵⁴