. it is worth noting that the new square meters available have been reflected in more vacant office space, at more than 10 percent now. therefore, the rents have dropped, a tendency that is expected to continue in the coming quarters ( figure 12 ). about the financial situation of households, aggregate indicators ( i. e. borrowing and financial burden ) show slight changes lately. at june 2015, household debt amounted to 61. 6 percent of income, 0. 8 percentage points more than at end - of - 2014, remaining on an upward trend. the financial burden remained stable, closing at 14. 7 percent. the latest survey of household finances showed an increase in the financial burden of medium - to upper - income households with respect to 2011 ( figure 13 ). this occurs in a context where household default indicators remain stable. however, credits from family clearing houses ( which represent a low fraction of household debt, at 3. 4 percent ) continue to increase nonperformance. this situation, coupled with flawed management, drove one of these institutions to default on its financial and social commitments, triggering intervention by the supervising entity and starting a restructuring process. these events motivated an increase in the premiums on the debt issued by these institutions, but their effects on the rest of the financial system have been limited. still, we believe that steps must be taken to boost the convergence of the supervision models of these houses, among others, in order to enhance their corporate governance and their credit risk management, to reduce the probability of new instability episodes. in the banking system, credit activity is growing moderately, except for mortgage loans. corporate and consumer loans continue to grow slowly. on one hand, the slowdown of the commercial portfolio is consistent with the economy ’ s cycle, which coincides with the reduction bis central bankers ’ speeches in demand revealed by the bank credit surveys of the past few months. on the other hand, the consumer portfolio shows zero growth in the lower amount segments, usually associated with lower - income debtors. in the mortgage category, the greater expansion of debt comes from loans of more than five thousand uf, partly explained by the housing price dynamics. bank financial indicators show the sector losing strength. at the third quarter of 2015, roe dropped to 15 percent, largely because of reduced interest rate spreads. this reflects the shift in portfolio composition from higher - yield segments ( consumer and commercial ) to mortgage. the capital adequacy ratio ( car ) continued to decline, to slightly below 13 percent

, the higher the weight. the figure for risk - weighted assets ( rwa ) represents the sum of these risk - weighted positions. required capital, in turn, is defined as a percentage of rwa. there are two different approaches for setting risk weights. under the standardised approach, risk weights are prescribed for broad asset classes. under the model - based approach, by contrast, banks can use their own internal models to determine the risk weights for different assets. the credibility of rwa based on banks ’ internal models is increasingly being called into question by market participants, analysts and authorities worldwide. it is widely accepted that a bank ’ s risks can, in principle, be more accurately quantified using the model - based approach than using the standardised approach. yet banks ’ internal models are extremely complex and can vary widely between banks, owing to the use of different model choices and model parameters. this can result in different capital requirements for banks with a similar asset structure. this makes it difficult to accurately assess a bank ’ s resilience, and to compare one bank with another. bis central bankers ’ speeches to increase the usefulness and credibility of the model - based approach, in - depth analyses need to be carried out to determine whether and to what extent the model - based approach and the standardised approach lead to differences in rwa. the standardised approach does have shortcomings. yet, since it is independent of bank - specific modelling assumptions, it provides market participants with an additional point of reference for assessing both the level of and changes in model - based rwa. differences between the two approaches must be well explained and have a sound economic rationale. if the analysis does not reveal any substantial inexplicable differences, this will strengthen market confidence in the modelbased approach. otherwise, appropriate measures should be considered. this could, for instance, entail setting a floor for some model - based rwa, such as that recently introduced for banks in the us. another option would be to introduce a multiplier on model - based risk weights for specific positions, as already imposed by finma for some mortgage loans. efforts are underway at finma, supported by the snb, to analyse potential differences between the two approaches. in this context, the snb recommends that the big banks increase transparency with regard to their risks. this includes, among other things, publishing their internal measures of total risk. disclosing rwa according to the standardised approach