The London based think tank Open Europe says the exposure from Greece puts the ECB's balance sheet at risk. A small 4.25% drop in the value of the ECB's asset holdings could wipe out the whole capital base of the ECB, according to Open Europe. The ECB holds at present 75 billion euros of Portuguese, Greek and Irish bonds on its balance sheet. In the last 12 months the ECB has increased its capital base to 10 billion euros. The decision to buy Spanish and Italian bonds increases the risk. The ECB loses money if the borrowing bank goes bankrupt or the collateral of the borrowing bank loses value. During the negotiations for the eurozone debt deal in July 2011, the ECB obtained guarantees from eurozone governments for the collateral it holds from Greece. This increases the need for the European Financial Stability Facility to take on the role of buying bonds of troubled eurozone countries.