This is from one of the latest NBER papers:
"This paper investigates the negative effects of exchange controls on trade. To minimize evasion of controls, countries often intensify inspections at the border and increase documentation requirements. Thus, the cost of conducting trade rises.
The paper finds that a one standard-deviation increase in the controls on trade payment has the same negative effect on trade as an increase in tariff by about 14 percentage points. A one standard-deviation increase in the controls on FX transactions reduces trade by the same amount as a rise in tariff by 11 percentage points."
Read more here.
Think about the jobs that would have created if not for the FX control, think about the economic growth that would have gained as a result of higher export if not for the FX control, think about the additional political heat that would have created in the US if not for the FX control...
Mind boggling indeed.