The June quarter 2015 edition of the Reserve Bank of Australia Bulletin has an interesting article – Firms’ Investment Decisions and Interest Rates – which further erodes the mainstream economics claim that business investment is negatively related to interest rates in any continuous way. The implications of the RBA research are many. First, it further helps us understand why monetary policy (adjusting interest rates) is not a very effective way of managing aggregate spending. Second, the research undermines the validity of the mainstream claims that crowding out of private expenditure occurs when government spending rises. The paper finds that investment decisions by firms is not sensitive to interest rate variations within certain ranges. Third, it demonstrates that business investment is driven significantly by subjective sentiment rather than being an exact process driven by quantifiable metrics.