Linked from
The 19 pages that link to Black market, each with the reason it gives.
RationingRelated: Restricted supply can redirect demand toward unauthorized resale and exchange.
Drug prohibitionRelated: Bans can displace drug supply into unregulated, clandestine markets.
Capital controlsRelated: Binding currency restrictions can create unofficial exchange markets.
War communismRelated: Illegal exchange grew as official distribution failed to meet everyday needs.
ProhibitionRelated: When demand persists, a ban can shift supply into illegal markets.
Iranian rialRelated: Foreign currency can trade outside Iran’s official exchange mechanisms.
CaviarRelated: High prices and restrictions have made illicit caviar trade profitable.