Murray N. Rothbard
The Monetary Breakdown of the West
As dollars piled up abroad and gold continued to flow outward, the U.S. found it increasingly difficult to maintain the price of gold at $35 an ounce in the free gold markets at London and Zurich. Thirty-five dollars an ounce was the keystone of the system, and while American citizens have been barred since 1934 from owning gold anywhere in the world, other citizens have enjoyed the freedom to own gold bullion and coin. Hence, one way for individual Europeans to redeem their dollars in gold was to sell their dollars for gold at $35 an ounce in the free gold market. As the dollar kept inflating and depreciating, and as American balance of payments deficits continued, Europeans and other private citizens began to accelerate their sales of dollars into gold. In order to keep the dollar at $35 an ounce, the U.S. government was forced to leak out gold from its dwindling stock to support the $35 price at London and Zurich.
A crisis of confidence in the dollar on the free gold markets led the United States to effect a fundamental change in the monetary system in March 1968. The idea was to stop the pesky free gold market from ever again endangering the Bretton Woods arrangement. Hence was born the "two-tier gold market." The idea was that the free-gold market could go to blazes; it would be strictly insulated from the real monetary action in the central banks and governments of the world. The United States would no longer try to keep the free-market gold price at $35; it would ignore the free gold market, and it and all the other governments agreed to keep the value of the dollar at $35 an ounce forevermore. The governments and central banks of the world would henceforth buy no more gold from the "outside" market and would sell no more gold to that market; from now on gold would simply move as counters from one central bank to another, and new gold supplies, free gold market, or private demand for gold would take their own course completely separated from the monetary arrangements of the world.
Along with this, the U.S. pushed hard for the new launching of a new kind of world paper reserve, Special Drawing Rights (SDRs), which it was hoped would eventually replace gold altogether and serve as a new world paper currency to be issued by a future World Reserve Bank; if such a system were ever established, then the U.S. could inflate unchecked forevermore, in collaboration with other world governments (the only limit would then be the disastrous one of a worldwide runaway inflation and the crackup of the world paper currency). But the SDRs, combatted intensely as they have been by Western Europe and the "hard-money" countries, have so far been only a small supplement to American and other currency reserves.
All pro-paper economists, from Keynesians to Friedmanites, were now confident that gold would disappear from the international monetary system; cut off from its "support" by the dollar, these economists all confidently predicted, the free-market gold price would soon fall below $35 announce, and even down to the estimated "industrial" non-monetary gold price of $10 an ounce. Instead, the free price of gold, never below $35, had been steadily above $35, and by early 1973 had climbed to around $125 an ounce, a figure that no pro-paper economist would have thought possible as recently as a year earlier.
Far from establishing a permanent new monetary system, the two-tier gold market only bought a few years of time; American inflation and deficits continued. Eurodollars accumulated rapidly, gold continued to flow outward, and the higher free-market price of gold simply revealed the accelerated loss of world confidence in the dollar. the two-tier system moved rapidly towards crisis-and to the final dissolution of Bretton Woods. 
 On the two-tier gold market, see Jacques Rueff, The Monetary Sin of the West (New York: MacMillan, 1972).