@Dominions Son1. Measured for medical records? Have you ever gotten an accurate height measurement at the doctor? Taken with or without shoes?
2. Yes they do - and they lie about it. Men who are really 5'10" claim they are 6'. Personally, my wife who is just 5'4" has always envisioned herself as 5'6"
3.The most obvious is that people get shorter with age. Significantly shorter. See how much that height changes from year to year. I would bet that most people put the same height on their DL at 65 as they did at 20.
"Measured" isn't often better. You always see that the Netherlands has the tallest men in the world - over 6' on average. All from a single study of less than 100 university students.
ETA: A reference I left out
Introduction
Self-reported data on weight and height are much easier, simpler and inexpensive to obtain than measured values. Therefore, in many cases, self-reported data are used, but their validity may be questioned. Recent reviews1,2report a general trend to overestimate one's height and also to underestimate one's weight, especially by overweight or obese persons. Body mass index (BMI) values that are computed from weight and height are therefore also underestimated. These observations are confirmed for adolescents.3 The self-reported data can substitute for measured data for most purposes, especially if only means are used, since the correlations between self-reported and measured heights and weights are high.4β7 However, for other applications, such as health surveys (e.g. prevalence of obesity), clothing sizes., or input for ergonomic design, it is important to know how trustworthy the reported values are.
Many articles describe overall effects: over-reporting of height and under-reporting of weight. More specifically, a tendency toward the mean or 'flat slope syndrome',8,9 meaning overestimation of lower values and underestimation of higher values, is also reported frequently (see, for instance, refs. 4, 6, 7 and 10). Factors that are related to the accuracy of the self-reported data are gender, age7,10 and weight status (underweightedβobese).4,5
The present study investigates whether also regional differences exist with respect to the errors in reporting weight and height. Our specific aims are (i) to explore the effect of regional information in relation with gender, age and height or weight or obesity status on systematic errors in reporting weight and height, and (ii) to examine the same effects on the resulting calculation of BMI. The data used have been assembled by identical procedures in three countries (Italy, the Netherlands and North America).
https://academic.oup.com/eurpub/article/21/4/414/434809