I wonder if what I have in mind exists under some name.
Everyone knows the "performance history" charts that are supplied with virtually any mutual fund. All of them start with "100 imaginary money units invested N years ago", then the chart shows how those 100 units changed value over the course of time.
Every point computed relative to that starting date.
I'd be curious to see the "performance history" according to today's date, not an arbitrary date of the past.
Each point of the chart would answer this question: "had you invested 100 units N days ago, what would be the value of that investment today?". Hence the chart's last point would be 100. Just like the usual performance history chart starts at 100 at a point in the past.
I believe that such a chart would be very, very telling, especially in juxtaposition of the usual performance history charts. E.g. imagine your banker, showing you the typical fund which had a 50% increase 5 years ago, but remained relatively stable, maybe with large drops or highs over the last 4 years. Yet, all of it looks in the positive, since the starting point was very low.
Contrast this with how the chart would look like when the reference point is today rather than 5 years ago: it would be immediately apparent that investors who invested in this fund saw a vastly different performance according to when they entered. Some would be very positive, others would be very negative.
I start to suspect that "performance history" charts with a reference point in the distance past prevailed more due to marketing purposes (to make the average fund look better to the naked eye) rather than usefulness.
The inspiration of all this was from a coworker, who mentioned investing in a certain fund that I had invested to, and that his share was in the negative, while for me I only ever remember seeing it positive. Quite eye-opening.