financial crisis increased house affordability in these countries, this gain has been offset by the ongoing increases in house prices. for bis central bankers ’ speeches the inflections in the rate of leverage growth that we see in the chart after the crisis may be due to the macroprudential measures these countries implemented. such measures have allowed stimulative monetary policy to flow through to households with the capacity to borrow. 30 chart 13a and b draw on recent work by the imf, which shows that macroprudential policies in the form of maximum loan - to - value ( ltv ) or debt - to - income ( dti ) ratios have tightened across a broad range of countries over the past 10 years. 31 the imf ’ s research, as well as that of other economists, has found evidence suggesting that the tightening has helped to : • reduce the procyclicality of household credit and bank leverage ; • moderate credit growth ; • improve the creditworthiness of borrowers ; and • lower the rate of house price growth. the most effective macroprudential policies to date appear to have been the imposition of maximum ltv and dti constraints. 32 increased capital weights on bank holdings of mortgages have also had an impact. 33 while long - term evidence on these instruments is not yet available, permanent measures that address structural regulatory weaknesses and that are relatively straightforward to implement and supervise will likely be the most effective over time. in canada, we have had four successive rounds of macroprudential tightening, primarily in terms of the rules for insured mortgages ( figure 1 ). i ’ ll mention just a few of the highlights. the maximum amortization period for insured loans has been shortened from 40 years to 25. 34 ltv ratios have been lowered to 95 per cent for new mortgages, and 80 per cent for refinancing and investor properties. these latter two changes effectively eliminate new insurance for refinancing and investor properties. qualification criteria such as limits on the total debt - service ratio and the gross debt - service ratio, as well as requirements for qualifying interest rates, have also been tightened. 35 recent evidence suggests that these measures have resulted in higher average credit scores, which have improved the quality of mortgage borrowing ( chart 14a ). with respect to household credit growth, chart 14b, shows that the trend growth of mortgage credit declined example, chart 6 in the december 2014 financial system review shows that the affordability

margin calls in case of variations in the collateral market value. source : imf ( 2003 ), “ deflation : determinants, risks, and policy options ”, april 2003. bis central bankers ’ speeches decisively in the event of an excessive appreciation of the swiss franc. this policy was maintained throughout the first half of 2010. in spring 2010, the news on the state of the swiss economy turned increasingly positive although the forecast remained fraught with major uncertainties. it was not clear, for instance, that partial unemployment ( short - time work ) could be reabsorbed without a significant additional increase in the rate of unemployment. the recovery appeared to be on the way but was presumed to remain very fragile. at the same time, the sovereign debt crisis in europe was causing major tensions in financial markets. in general, markets were commonly afraid that the euro could face long term structural problems, the flight to safe investments was universal and the pressures on the swiss franc were substantial. the snb considered that, at that time, the swiss economy was unlikely to have gained enough strength to be able to withstand a further violent appreciation of the franc. such a development would have placed the swiss economy under such severe strains that the threat of a deflationary trend would have again come to the fore. the snb was not prepared to take this risk ; it resisted an excessive appreciation of the franc and in so doing was led to acquire large quantities of foreign exchange. as is now well known, the eu authorities came up with a “ shock and awe ” package10 that, after some hesitations, market participants accepted as providing some reassurance, although not a complete and final solution to the european periphery debt problem. by the end of may, the pressures on the franc started to subside. taking stock of these developments and of the visible strengthening of the recovery of the swiss and global economies, the snb considered in its june monetary assessment that the threat of deflation had largely disappeared. a further appreciation of the swiss franc was no longer such a threat to price stability and the economy as it had been previously. in the second half of the year the snb thus refrained from carrying out further interventions on the foreign exchange market. one can summarise this historical episode as follows. from march 2009 to the end of the year the snb decided, in view of providing the most appropriate monetary conditions to an economy in recession, and given that traditional monetary