Why are you referring to rand performance in reference to unit trusts? Although some funds will no doubt be indirectly affected by the strength or weakness of the rand many others are not. Unless you are considering investing in a dollar or euro based fund?
Remember unit trusts (now referred to as collective investments) are merely investment vehicles whereby investor's funds are pooled together and the fund manager then invests these funds into different assets (equity, bonds, property, cash and their derivatives) according to the chosen fund's mandate (ie an equity fund would invest primarily in equities, property fund in property etc). The amount you invest will buy you units in this investment pool. The price of each unit is dictated by the market value of the asset that have been invested in within the fund. As the market value of the asset increase so does the unit price.
Trying to time the markets is not the way to go. It works well in hindsight but the reality is that you are unlikely to time the market accurately every time. Below are some numbers regarding timing the market that were shared at an investment meeting a few years back. This does not apply directly to South African unit trusts specifically but the principle would obviously remain the same:
Black Monday, October 19th 1987
Dow Jones lost 22.6% in one day and a further 18% the next
How long did it take to recover?
It took just under 2 years to recover, but 1987 itself was still a positive year for the index
9/11, September 11th, 2001
NYSE closed for 4 trading days (longest closure in history)
Dow Jones lost just under 7% in that time and declined a further 6,5% in the days after it re-opened
How long did it take to recover?
Recovered to pre-9/11 levels by mid-November
The JSE recovered in 8 days
The question to be asked is when would you have decided to re-enter the market? Would you have missed part of the recovery? Below is a table showing the effect of missing the best performance days over 10 years on the MSCI Europe index versus remaining fully invested:
If you could just hit all the good days and miss all the bad ones that would be great but many spend their lives trying to do this and fail so the likelihood of a lay person getting it right in unlikely. The old adage goes that it is not
timing the market that is important but rather
time in the market.