As part of the first amendment to its articles of agreement in 1969, the IMF developed a new reserve instrument called special drawing rights (SDRs), which could be held by central banks and exchanged among themselves and the Fund as an alternative to gold. SDRs entered service in 1970 originally as units of a market basket of sixteen major vehicle currencies of countries whose share of total world exports exceeded 1%. The basket's composition changed over time and presently consists of the U.S. dollar, euro, Japanese yen, Chinese yuan, and British pound. Beyond holding them as reserves, nations can denominate transactions among themselves and the Fund in SDRs, although the instrument is not a vehicle for trade. In international transactions, the currency basket's portfolio characteristic affords greater stability against the uncertainties inherent with free floating exchange rates. Special drawing rights were originally equivalent to a specified amount of gold, but were not directly redeemable for gold and instead served as a surrogate in obtaining other currencies that could be exchanged for gold. The Fund initially issued 9.5 billion XDR from 1970 to 1972.