You pose an interesting question.

Part of the problem with 'proving' whether or not business ethics actually works is that many of the issues relating to business ethics are qualitative, rather than qualitative in nature.

Consider some of the commonly sighted benefits of positive ethical behavior:

(1) more effective working relationships with a range of key stakeholders (customers, suppliers, employees, the general public, etc);

(2) Avoidance of penalties, such as fines or compensation claims; and

(3) Avoidance of stricter government regulation.

In relation to each of the above factors, the magnitude of the impact is difficult to quantify. Accordingly, a considerable degree of subjectivity is required in assessing their value.

Therefore, the one cannot 'prove,' in an objective fashion, that the benefits of positive ethical behavior outweigh any costs involved in such behavior.

However, the benefits of positive ethical behavior are real, and underestimating the value of such benefits would not appear to be a wise business decision.

Cheers

Andrew