Three of the big four banks have recently reported half-yearly results, and Commonwealth Bank (CBA) gave a quarterly update on Thursday. Increasing interest rates should allow the banks to improve their net interest margins which have been crushed as rates have fallen close to zero; record low rates and a resurgent economy have however helped the banks keep bad and doubtful debts at extremely low levels. Westpac (WBC) remains the favourite among nabtrade investors, having been the most popular buy of the big four for nearly 18 months, however, its recent pop has seen considerable trimming. More popular recently has been Macquarie Group (MQG), a high conviction stock that enthusiasts will buy in a pullback. At less than $180, there have been plenty of enthusiasts for Macquarie this week; the stock was closing in on $220 in January.