Not Much Fits

Anthropometry is defined as “the study of human body measurement for use in anthropological classification and comparison.” This study is often used by designers when working on all day to day objects and surroundings.

It seems that when it comes to design, most designers use the parameters for those above the 5th percentile and below the 95th percentile. The simple explantion of this is that the 90% of the population who are considered “normal” or “average” have things designed with them in mind. The rest of us, (the very short, below the 5th percentile and the very tall above the 95th percentile) are considered unimportant and therefore not even considered.

If you would like to read the full explanation of this have a look at this.

“If you are more than 95th percentile height or less than 5th percentile, we predict that some everyday objects do not always seem quite the right size for you. Just as you were able to compare your height with others in a given population, it is also possible to make such comparisons for other dimensions such as arm length, hand grip span, seated elbow height etc. Those whose build puts them towards the one extreme or the other will be familiar with the problems of using awkward sized objects. This is probably because the designers of these things have chosen limits outside your height range in their design.

Suppose you measure the heights of all the people who live on your street. You would expect some variety in their heights, and perhaps the occasional very tall or short person – but by and large the people will tend to be a “normal” or “average” sort of height. By measuring these neighbours you would understand the distribution of their heights and you could use this information to make a reasonable guess about the height distribution of all the people in your area or town. This is how the principles of statistics are used in anthropometry.

If we plot a graph, with height along the X axis, and the number of people who are that height as the Y axis, we see a bell-shaped, or “Gaussian” curve. This shows that most people are “about average” height, but a few are very tall or very short in comparison to everyone else. We can split the X axis up into sections which show what percentage of the population are that height (or more/less). These divisions are called percentiles. For instance, 95% of the population are smaller than or exactly the 95th percentile height (so only 5 percent are taller).

By using this concept, designers can specify in advance what proportion of a population they want their design to satisfy or fit, and can then use the appropriate percentile dimension to use in the design. This choice will be influenced by the importance of getting the design right. For a safety feature, such as the size of an aircraft emergency exit, it is important that everyone be able to use it, and so the designer will choose very strict limits, ensuring that the vast majority of the passengers will be able to escape. However, accommodating the extremes of a population can be very time consuming and expensive, and there are, after all, only a very few people who will benefit from the consideration. Because of this many people will use the 5th and 95th percentiles to define the range which they “accommodate” with their design. This will ensure that at least 90% of the population will be suited by the dimensions.”

So now you know why as a minority, we (the tall) are ignored. If we assume those above the 95th percentile account for 5% of the population.
This would mean 5 in 100 people are outside this range.

In other words:
There are 50 of us in 1000.
500 of us in 10,000.
5000 of us in 100,000.
50,000 of us in 1 million.

There are rougly 60 million people live in the UK, so that means there are 3 million of us in the UK at or above the 95th percentile- being ignored by the designers!