The rise in the debt burden of the household sector is most pronounced among older and higher income families, and the factors giving rise to this trend may induce a further rise in the level of indebtedness the Reserve Bank of Australia said yesterday.Ric Battelino, deputy governor of the RBA, told the Finsia-Melbourne Centre conference yesterday that the rise in debt during Australia's long boom "has been overwhelmingly driven by those households that had the greatest capacity to service it - the middle-aged, high-income group."It is not surprising, therefore, that this rise in debt has exhausted neither the collateral nor the debt servicing capacity of this group, or the household sector overall."Battelino cited RBA estimates, presumably drawn from recent census data, that more than 80 per cent of households in the top half of the income distribution have some type of debt, compared with only 30 per cent of those in the lowest decile.He said that "it seems that debt is one of those products, like education and health, which has a high income elasticity of demand. It would be a mistake to conclude that a rising ratio of debt to income is necessarily a sign of financial stress among households." Battelino said about three quarters of the increase in owner-occupier debt over the decade to 2006 was attributable to households in the top half of the income distribution. He said "if comparable figures on debt associated with investment properties and margin loans were available, they would almost certainly further skew this distribution of debt."He said a large contribution to the increase in household indebtedness has come from households  with members aged 45 to 65. Within this group the proportion of households carrying owner-occupier debt increased from 25 per cent to 38 per cent.