Two property investments report different percentage values for the same year. If your stakes differ greatly, their simple average will not correctly describe your overall result. First, the euro changes must be matched to the actual capital amounts.
Define a comparable period and a notion of holdings
For our completely fictional case both investments are held at the stated amount exactly at the start of the year. There are no further deposits, distributions, withdrawals, costs or taxes. The stated percentage values each describe the total change in value up to the end of the year. They are not current provider figures.
In a real report it must first be clarified whether the figures even share the same basis. A price gain without distribution, a total return and a reported distribution rate are not interchangeable without examination.
Prepare your own euro calculation
Investment A contains 90.000 euros. Its assumed change in value is plus ten percent, i.e. plus 9.000 euros. At the end it stands at 99.000 euros.
Investment B contains 10.000 euros. Its assumed change is minus twenty percent, i.e. minus 2.000 euros. The end value is 8.000 euros.
Together 100.000 euros were invested, and the end values amount to 107.000 euros. The combined change is therefore plus 7,000 euros or seven percent. The simple average of plus ten and minus twenty percent would, by contrast, be minus five percent. That would pretend that both original stakes had been equally large.
Keep the weights verifiable
The same result can be written using the initial weights: 90 percent times ten percent plus ten percent times minus twenty percent equals seven percent. What matters here are the expressly specified initial amounts without intermediate payments. With later deposits or withdrawals a different suitable evaluation is required; the simple weighting must not be continued without verification.
Performance is not yet a paid-out purchase reserve
Even the correctly calculated end value of 107.000 euros initially remains modelled within the investments. Whether money could be made available from this for a property purchase requires the actual sale or payout conditions. A correctly calculated gain in value is not a confirmed cash receipt.
The total value also does not indicate whether the investments are sufficiently independent or suitable for your objectives. Risks and personal capacity to bear them must be assessed separately.
The method fulfils a narrower task: it uses your own stakes instead of an unexamined average of the percentages in the year-on-year comparison. This allows an actual result to be explained in a verifiable way, without turning it into a forecast for coming years.