You know those height charts that parents and grandparents keep of their children and grandchildren? Every time we visited my grandmother, we had to stand against a door frame and have our heights marked (and dated). The house is gone and to the best of my knowledge, there are no photographs of the height charts of me and my sister.
We did the same thing with our granddaughters but at least had the good sense to take photos of them before we moved.
Ms. Eclectic and I are going to start a new version of height charts. We are aging, and as we age, we are losing height [digression: which means, of course, that our BMIs are going up despite weight loss, dammit.]. I've had some compression fractures in my vertebrae. And one of our granddaughters says she is now taller than Ms. Eclectic despite not having grown any more herself. Along this same line, I can recall being surprised by how short my mother seemed in her later years, and it wasn't just because I had grown.
So here is our suggestion. When people reach the age of about 45 or 50, they should put up height charts designed for children. Then as they [we] shrink, we can keep track of the shrinkage on the height chart.
Addendum: We actually started something like this the other day. We marked our respective heights on a door jamb. And then we measured the heights of the marks. Indeed, we have both lost some height from our peak heights.
probably not much of a market for this product.