Any received wisdom on the significance of Australia's worsening terms of trade for banking sector credit quality is yet to percolate into the credit quality settings at Commonwealth Bank. In the half year to December 2015 CBA lifted its provisions for impairment by a trivial one per cent to A$3.67 billion, a level that is five per cent less than warranted one year earlier.Macro factors, such as those whirling through the resources sector, did produce an increase in economic overlays but these were offset by other factors such as a "continued run-off of troublesome and impaired loans" at Bankwest.One nod to the impact of presumed economic strife was the concession that "higher home loan arrears and losses in Western Australia and Queensland [were] predominantly driven by deterioration in mining towns, and arrears in the personal loans portfolio."Total provisions for impairment losses as a percentage of total loans CBA set at 0.55 per cent, down one basis point over six months and down seven bps over one year.