Central bank balance sheets are expanding at what some say is an alarming pace. Can this cause the next bubble to form and burst?

JP Morgan estimates G4 (U.S., Japan, euro zone and Britain) balance sheets are now around 24% of GDP combined, with around 11% of GDP comprising bonds held for monetary purposes.

“The recent pace of balance sheet expansion is the fastest since the immediate aftermath of Lehman, largely down to the ECB. The increased BOJ purchases, more QE in the UK, and 200 bln euros upwards of increased ECB lending from this month’s LTRO together point to a further $600bln+ rise in G4 central bank balance sheets this year, to around 26% of GDP.”

Outside G4, Switzerland is a country which saw a massive expansion in its central bank balance sheet. And because of its huge holdings, its balance sheet has been very volatile.

The Swiss National Bank suffered a loss of 21 bln francs last year — its biggest ever — due to currency interventions to weaker the Swiss currency. It expects to swing back to a profit of 13 bln francs this year.