The Shadow Economy and Morals: A Note

If the established rules are obeyed spontaneously in an economy,
this increases economic efficiency since the uncertainties,
monitoring costs and incentive problems induced by opportunism can
be avoided. Opportunism will be increasedby increasing the
incentives for unlawful behaviour, however, and a slight increase
in these incentives might cause a cumulative and self-nourishing
breakdown of morals. The dangers of the growing shadow economy are
louring here.