The central bank delivered its second monetary stimulus in three months by topping up its asset buying scheme, which is among programmes it has put in place since last year to battle the economy's ills such as persistent deflation and sliding potential growth. The central bank's policy target is the overnight call rate, now set at a range of zero to 0.1 percent. With rates effectively at zero, the BoJ's key monetary policy tool is the asset buying programme, under which it purchases government bonds and private debt. The total size is now set at 55 trillion yen ($705 billion) of which 20 trillion yen is for asset purchases, with the remainder for market operations. Oct 2011 Boosts asset buying fund to 55 trillion yen Aug 2011 Boosts asset buying fund to 50 trillion yen Mar 2011 Increases asset buying fund to 40 trillion yen Oct 2010 Sets up 35-trillion yen asset buying programme. Cuts overnight call rate to 0-0.10pc. Pledges to keep zero rates until prices stabilise Aug 2010 Further boosts fund for fixed-rate market operations Mar 2010 Expands fund for fixed-rate market operations Dec 2009 Creates fund for fixed-rate market operations Dec 2008 Cuts overnight call rate to 0.10pc Oct 2008 Reduces overnight call rate to 0.30pc Feb 2007 Lifts overnight call rate to 0.50 pct July 2006 Ends zero rate policy. Sets overnight call rate at 0.25pc Mar 2006 Reverts to policy targeting interest rates. Overnight call rate effectively set at zero Mar 2001 Adopts "quantitative easing" policy Feb 2001 Cuts overnight call rate to 0.15pc Aug 2000 Ends zero rate policy. Sets overnight call rate at 0.25pc Feb 1999 Adopts zero rate policy Pledges to guide call rate "as low as possible".