Performance ratios – Why are these used?

Accounting and financial management have often been regarded as the most complex aspects of managing a business. The numbers are usually big, the formulae confusing and there are so many regulations. It is fine for the Director of Finance/CFO and his/her team but what about the other stakeholders, especially average investors and the managers actually running the show. How can they ensure that their investment is safe or their performance is in line with organizational goals?