true for 20 years.
I'm quite interested in how to change this structure to account for someone retiring at below age 45 to live for far more than 20 years, ie highest chance of indefinite, say 60 years, such that they never reach 0 balance.
I use a pretty sophisticated piece of retirement planning software using Monte Carlo simulations to answer these questions.
I ran the numbers for a 45 year old male in average health (so the income has to last for life of individual only- no dependent spouse).
The numbers are expressed as a % of retirement savings at retirement date: so 4% means for someone with R1,000,000 in savings, they can draw down an income of R40,000 in the 1st year and increase this by inflation each year in future. To get annual income multiply % by total savings.
I first calculate how much income can be derived if savings are used to buy a guaranteed inflation protected annuity - this is theoretical, I don't know if any insurers in SA sells these to people as young as 45. It is just to get a feel for what the theoretical maximum income is that would last till death.
Guaranteed inflation protected annuity for 45yo male : 4.62%
What follows are results if savings are invested and income drawn down over lifetime - in this case there can be no 100% guarantee as with the guaranteed annuity above. The retiree keeps control over his funds, but bears the full investment/longevity risk. So the outcome has to be expressed in terms of probability of success (success = savings outlasts retiree/ failure = runs out of money whilst still alive):
Below follows the success probabilities for different levels of risky investment portfolios @ 3%,3.5%,4% and 4.5% initial drawdown levels:
Conservative portfolio: 92%, 71%, 51%, 38%
Balanced portfolio: 98%, 94%, 88%, 79%
Aggressive portfolio: 93%, 89%, 84%, 78%
So the sweet spot would be a Balanced portfolio (taking more risk increases the number of failures) drawing down between 3-3.5% in 1st year.