Central banks made their largest purchases of gold in four decades in the third quarter after a sharp drop in prices in September spurred buying to diversify reserves.

The scale of the purchases, at 148.4 tonnes on a net basis, was far bigger than previously disclosed and puts central banks on track to buy more gold than at any time since the collapse of the Bretton Woods system 40 years ago, when the value of the dollar was last linked to gold.

Analysts said the buying, led by emerging market central banks intent on diversifying their foreign exchange reserves, helped explain the rebound in gold’s price from a low of $1,534 a troy ounce in September. “Central bank buying tends to follow a different heartbeat than pure investment purchases of gold,” said Marcus Grubb, head of investment at the World Gold Council. “It’s often based on targets set earlier in the year on gold as a proportion of foreign exchange reserves.”