Last year, the fund had excellent performance at 53%. But, in the past three years, the average annual return was 20%. What did it do in years 1 and 2 to bring the average return down to 20%? Some simple math shows us that the fund made an average return of 3.5% over those first two years: 20% = (53% + 3.5% + 3.5%)/3. Because that is only an average, it is very possible that the fund lost money in one of those years.

It gets worse when we look at the five-year performance. We know that in the last year the fund returned 53% and in years 2 and 3 we are guessing it returned around 3.5%. So what happened in years 4 and 5 to bring the average return down to 11%? Again, by doing some simple calculations we find that the fund must have lost money, an average of -2.5% each year of those two years: 11% = (53% + 3.5% + 3.5% - 2.5% - 2.5%)/5. Now the fund's performance doesn't look so good!

It should be mentioned that, for the sake of simplicity, this example, besides making some big assumptions, doesn't include calculating compound interest. Still, the point wasn't to be technically accurate but to demonstrate the importance of taking a closer look at performance numbers. A fund that loses money for a few years can bump the average up significantly with one or two strong years.

It's All Relative
Of course, knowing how a fund performed is only one third of the battle. Performance is a relative issue, literally. If the fund we looked at above is judged against its appropriate benchmark index, a whole new layer of information is added to the evaluation. If the index returned 75% for the 1 year time period, that 53% from the fund doesn't look quite so good. On the other hand, if the index delivered results of 25%, 5%, and -5% for the respective one, three, and five-year periods, then the fund’s results look rather fine indeed.

To add another layer of information to the evaluation, one can consider a fund’s performance against its peer group as well as against its index. If other funds that invest with a similar mandate had similar performance, this data point tells us that the fund is in line with its peers. If the fund bested its peers and its benchmark, its results would be quite impressive indeed.

Looking at any one piece of information in isolation only tells a small portion of the story. Consider the comparison of a fund against its peers. If the fund sits in the top slot over each of the comparison periods, it is likely to be a solid performer. If it sits at the bottom, it may be even worse than perceived, as peer group comparisons only capture the results from existing funds. Many fund companies are in the habit of closing their worst performers. When the "losers" are purged from their respective categories, their statistical records are no longer included in the category performance data. This makes the category averages creep higher than they would have if the losers were still in the mix. This is better known as survivorship bias. (Learn more about survivorship bias in The Truth Behind Mutual Fund Returns.)