Investors will examine how much Commonwealth Bank of Australia has managed to offset pressure on its profit margins through last year's mortgage interest rate hikes when the country's biggest bank reports its first-half profits on Wednesday. With banks competing fiercely for borrowers, profit margins will be a key focus for CBA, which is predicted to deliver a first-half profit of more than $4.7 billion - an annual increase of about 2 per cent - and an interim dividend of $1.98 a share, consensus estimates indicate.