Moran Diagrams

Overview

Moran diagrams are a type of Venn diagram used to measure the imbalance of discrimination across two groups of people.

 

Structure

The outer boundary of the diagram is a circle, which is split vertically into two distinct “object” groups.

A “subject” group, representing the affected population, runs across the circle and overlaps the object groups.

The line above the subject group is called the “discrimination line” and indicates whether the discrimination is balanced or one-sided. Since the diagram is to-scale the angle of the line can be measured to quantify the magnitude of unfair discrimination.

 

Example

The progression of suffrage in the UK

Through the 1800s more men were given the right to vote and this increased the magnitude of sexist discrimination. From 1832 to 1884 the discrimination line became steeper. Only in 1918, when most women were given the right to vote, was the level of discrimination reduced. Equality[1] was finally achieved in 1928.

 

Relevance

Moran diagrams are designed to encourage critical thinking.

In 2016 the UN published a report on childhood education. There are 263 million children worldwide missing out on education; 130 million girls and 133 million boys. The issues that prevent most children attending school are poverty and war.
In 2018 the statistic “130 million girls” became a headline in the UK news. Politicians and journalists called for more to be done to tackle sexism in education. In the intervening years governments worldwide have set up and funded projects to tackle the sexism that prevents girls being educated.

We can measure the amount of sexism with a Moran diagram, using the data from that 2016 UN report.

130 million girls and 133 million boys are out of school

The discrimination line shows there is an imbalance that affects girls more than boys, however, the impact of poverty, war and other factors is visibly more significant.

1% of girls are out of school due to sexism

Most girls are out of school due to other factors. Focusing on sexism and tackling sexist inequality ignores the vast majority of girls and all boys.

The UN focuses its research on the inequality group, not the majority group. We are failing our children because we label a shocking statistic[2] “sexist” without understanding the context by asking “how sexist?”

The same UN report highlights other issues, one being the number of children who never go to school: 15 million girls and 10 million boys. These children never learn to read and write.
The discrimination line on this diagram is visibly sloped to one side. The level of sexism is more significant. This is the issue where sexism needs to be addressed.

15 million girls and 10 million boys will never go to school

 

Key Concepts

 

Subject Group

This subject typically divides the population into two groups - affected and unaffected.

Multiple subjects can be overlaid to compare differences in bias, but typically one subject is chosen.

 

Equality Line

Before the affected population is split into object groups the line above the affected group is called the equality line.

If the two object groups are the same size then the equality line will be flat/level.
If the two object groups are different sizes then the equality line will be tilted such that both groups have an equal proportion of their populations.

 

Object Groups

The circle is split vertically into two object groups.
NOTE: This is NOT a Pie Chart. The dividing line is vertical, not radial.

 

Discrimination Line

The line above the affected group is called the discrimination line.
A steeper line means the discrimination is more unfair and biased.

 

Discrimination Angle

The angle between the discrimination line and the equality line quantifies the bias between the two object groups - aka the amount of unfair discrimination.

 

Issues

 

Size is Not Severity

Severe issues can affect small sections of the population. A Moran diagram will show the affected group is small but this does not belittle the severity of the problem.
e.g. this Moran diagram shows children who have never been to school.

25 million children will never have a chance to enter school

The percentage of children is low but the impact is great; these 25 million children will never have the opportunity to read or write.
Remember that Moran diagrams are used to measure imbalance between groups, not the severity of the problem. A small subject group does not mean the problem is not serious.

 

Not the Whole Population

Moran diagrams do not often show the whole population. The circle only shows two object groups which may be two of many groups.

Use a Hughes diagram to look for imbalance across more than 2 groups.

 

Handling Smaller Object Groups

If one object group is significantly smaller than the other then the equality line becomes acute (less flat).
Some investigation is needed to check the impact of the angle of the equality line.

 

Nomenclature and Origin

Moran diagrams are named after Caitlin Moran, a feminist author and journalist.

The diagram originated in 2018 after a story about girls’ education made the UK news for several weeks. The headline “130 million girls are missing out on education” was repeated in numerous news articles and declared as sexist but a comparative figure for boys was always missing.
I researched the subject and was shocked to find the number of boys is higher than girls.

This reminded me of something Caitlin Moran once remarked, “You can tell whether something is sexist by asking, ‘Does this happen to men as well?’” paraphrased from [3].
To visualise the comparison I drew a Pie chart that included the whole population and then modified the chart to highlight the level of discrimination for each sex.
Although Moran diagrams are a subtype of Hughes diagrams, Moran diagrams were created first. Originally called Hughes diagrams, the name was changed to Moran after Hughes diagrams were created in 2020.

 


[1]
Equality does not require everyone in the population to be included. A flat line at any location on the diagram would indicate equality.

[2]
The statistic “130 million girls” has been the catalyst for many UN reports on sexism found in education in numerous regions of the world. Sexist discrimination is clearly a problem but only accounts for that small proportion of girls out of school.

[3]
Caitin Moran, How to be a Woman
You can tell whether some misogynistic societal pressure is being exerted on women by calmly enquiring, ‘And are the men doing this, as well?’