There is a thumb rule that Debt investment percentage should = age and Equity investment percentage should be 100-age . The more younger you are you should be more in equity . Alternatively the older you are your investment should be more in debt. We should take not take the mathematical proportion with complete rigidity but rather than evaluate profile of the individual . Thumb rule is relevant only when the networth or income level is inadequate to meet the day to day livelihood  . Does investment in debt make any sense for Mr Amitabh Bacchan or Mr Ratan Tata who are not young .

Income and Job stability is the key thing before thinking on portfolio allocation in debt . Lets take an example of an individual working in Government organisation , PSU and in a big reputed private sector brand like TISCO, TELCO , Infosys . Does he carries income risk or job risk . In my view No. His monthly income is there to take care of his routine expenses . For such investors opportunity of maximising gain should be the investment decision making .

Many experts also say when you have retired your investment should be almost all in debt . Again we need to look why . Its because may be you are dependent on that money in form of either dividend or withdrawal to meet your both end meet . Lets take present day example. Equity is giving or expected to give higher return than debt . So till that is happening or expected to happen  why one can not be in equity mutual fund and opt for monthly Systematic Withdrawal Plan from Equity MF scheme rather than investing in debt mf scheme and opting monthly SWP from debt MF . Take an example — equity mf is giving a return of 13 to 18 % CAGR and debt MF 8 to 10% CAGR .  You are adding some 3 to 5 % extra return in Equity fund which creates a bigger base on year to year and money grows faster vis a vis debt fund . Also for same amount withdrawal from both type of schemes the corpus left in debt will reduce faster than in equity fund i.e when in equity fund sustenance period is longer .

Proportion of equity is not what someone should decide while doing asset allocation. Its the minimum proportion of debt to meet basic need and also giving a mental comfort level to be decided  . Rest all should go to growth asset. Minimum requirement will vary from individual to individual but the basis of decision should be similar. You should have debt investment to ensure you get the quantum of amount you require in short to mid term . Any need of money required in next 3 year should not be left to market risk but to be safe . For a period 3 to 5 year again one has to look at the market situation and take a call . So decision can range from debt to hybrid to equity i.e perception on probability of loss  due to market risk . Beyond 5 year no reason to worry on asset risk but go for equity. Having said all these there is a need to evaluate year to year performance of both asset i.e debt and equity. If equity showing a declining trend for 2 consecutive year then you need to understand the factors which is leading to that. If the factors are there to stay for long then still keep safety rule of 3-5 years and not beyond that .