Algorithmic traders exacerbated volatility in the Swiss franc/euro exchange rate that arose when Switzerland’s central bank unexpectedly removed its currency cap in January 2015, according to new analysis.

In a shock move three years ago, the bank decided to decouple its franc from the European single currency. The cap had been in place since 2011 and had essentially pinned the currency at 1.20 francs per euro. The value of the euro collapsed as much as 30% versus the franc — and inflicted pain on many banks, trading firms and investors.