Most of those keen to compete against themselves in the Standard Chartered Mumbai Marathon (SCMM), held each year on the 3rd Sunday of January, will have submitted their registration by now – a few days after registration opened. Some will have registered for the first time, for others this will be a regular feature of their running calendar.

Background
A few months ago I shared, with friends, this graphic depicting the mean and median times of male and female runners in the ‘open category’ of the half marathon of 2014.

The mean is simply the average of numbers.  The median is ‘the middle one if you were to order them in order of size’ – ideal for comparing data where there are very large or tiny ‘outliers’ that might skew the average away from a fair representation of the typical candidate. Using the middle number, i.e. the median, as a representation often does a better job than the average.

Curiosity
I was curious, as were others, as to what has happened in the last few years, say between 2010-2014 (5 Mumbai Marathons) for the various categories of non-elite runners.  This short article is a fun words-and-pictures piece to give some colourful answers.

The Categories – Age/Gender Based
For the sake of prize distribution, the SCMM has the following age categories:

Winsorising – Gets rid of outliers
A half marathon, even if walked at a stroll should be completed within 4.5 hours – the world record, when run, is 58 minutes 23 seconds. So, the first thing I did was remove records where the completion time was more than 4.5 hours. There were a tiny handful of records that were excluded as a result.

The Number of Runners – Doubled!
There has been a doubling of numbers running the half marathon over the 5 race-year period. Whatever be the reasons, the growth is encouraging even if absolute numbers are a tiny fraction of the city’s or country’s adult population.

Average Racing Times – Younger isn’t always better!
If someone asked me “which of these categories is fastest on average?” my immediate reaction would be “the younger runners” i.e. male runners aged 18-45 (Men Open) or female runners aged 18-40 (Women Open). However, the data suggests something quite different which is easily explained by a combination of self-selection bias and survivorship bias.  And the conclusions are not the same for 2010 and 2014. Here are the average times in increasing order:

Median Racing Times – Younger is still not better!
As I explained, the average is often tilted away from a ‘fair representation’ if there are too many very fast or too many very slow runners. So, we can look at the median completion times instead. This means ordering each category in increasing times and then picking the runner in the middle as a representative of the sample. In that case, this is what we see:

It’s great to see that completion times have been improving for all categories, on average, or for the ‘middle runner’.

The Top 10%
If we now focus on the top 10% of runners in each category (yes, it doesn’t mean much for specific cases, when the sample sizes are tiny e.g. Women Super Veteran) and look at the slowest runner in that top 10% then we see:

Here’s a pictorial representation of the slowest runner in the top 10% in each category, along with a representation of the number of runners in each category.

Interestingly, even as the sample size has grown larger, the slowest of the runners in the top 10% of the Women Veteran runners is still a little faster than her younger counterpart in the Women Open category! And, now the top 10% of men whether below age 45 (Men Open) or below 55 (Men Veteran) can finish within the golden “2 hour” time.

The Bottom 10%
What is even more interesting is to notice that, among the slowest 10% of participants, the fastest of these slow participants have become faster:

What might this mean?
One could analyze the data in more detail and test various hypotheses.  For me the most simple observations are satisfying. As someone interested in making the world healthier, seeing such an improvement, albeit in just a tiny pocket of society is encouraging. Not only have the number of participants increased, but the overall level of fitness, when measured along this narrow dimension, has also increased.

Optimism and Hope
If it is true that the Standard Chartered Mumbai Marathon is a catalyst for improving the wellness of the city and beyond, may it continue to thrive.

Puru

Dr Purnendu Nath spends his waking hours focusing on helping individuals and organizations reach their goals, to make the world a better place. He speaks, writes and advises on topics such as finance, investment management, discipline, education, self-improvement, exercise, nutrition, health and fitness, leadership and parenting.