"We expect further margin erosion in the first half of fiscal 2024, as the sector continues to be impacted by deposit/mortgage competition and adverse deposit mix shifts," analysts at investment and advisory firm Jarden wrote in a client note. National Australia Bank (OTC: NABZY ) (NAB), the second-biggest mortgage lender and biggest business lender, is set to report a nine-basis-point narrowing in its first-half net interest margin when it begins the reporting season on May 2, with cash likely falling as much as 13%, analysts estimated. "As the economy slows at some juncture, we expect that NAB as the largest business bank will be at a structural disadvantage versus peers," wrote Citi analysts, who recently downgraded their recommendation on Big Four shares to "sell". "As business credit slows and becomes more competitive, relative momentum will disappoint and put pressure on (NAB's) expanded premium valuation."