The music swells. The lead singers hit their top notes. The rest of the cast join in the final chorus. The last bars of the song are greeted with thunderous applause. The actors leave the stage, and the house lights go up.
It's the interval in a sold-out West End musical. The audience stretch and shuffle in their seats. Time to pop to the loo and get a drink.
Ten minutes later, in the bar. The men, bladders safely emptied, are relaxing with a glass of wine. The women, however, are nowhere to be seen. They're still queuing for the loo. They'll be lucky to make it back into the auditorium in time for the second half, never mind get a drink.
What happened there? Did the theatre get anything wrong? They know that their audiences are equally split between men and women, so they provided equal numbers of toilets for men and women. That's fair, isn't it? What's the problem?
The problem of the queue for the ladies' loo is a very good way to explain the difference between equality and equity. These two words sound very similar, but the concepts they describe are very different. The theatre, in its toilet provision, acted on the basis of equality; that is, they treated everyone the same, by providing toilets on an equal basis to men and women. However, they didn't take into account the fact that, in the toilet department, men and women's circumstances are not the same. Without going into the anatomical details, women need longer. Hence the queues. If the theatre was operating on the basis of equity, it would provide men's and women's toilets not on the basis of the numbers of men and women who come to their shows, but on the basis of men's and women's different needs, meaning there'd be more women's toilets than men's. (Which, incidentally, would probably lead to higher takings at the bar.)
Equality treats all people exactly the same, taking no account of their present or past circumstances. Equality argues that this approach is clear, simple and fair.
Equity looks at the circumstances, past and present, of people and groups, and makes adjustments to take into account those circumstances. Equity argues that this approach is fairer than equality, because it corrects existing inequalities.
Neither approach is 'right'. Which approach you take depends on the particular issue. Equality and equity are very useful concepts in debating, as so many debates come down on a split between equality vs equity.
Let's look at some examples.
This house would require Oxford and Cambridge to admit a minimum of 90% of students from state schools.
Equity says that this is a necessary move to adjust for the advantages that privately educated students have over equally talented state school educated students; equality says it is unfair because it discriminates against private school students who have achieved the necessary grades, and ineffective as it will exclude talented students from private schools.
This house would require countries which have profited from slavery to pay reparations to countries whose people were enslaved.
Equity says that this is an act of justice. It is needed to correct the economic inequality between rich and poor countries, which was caused by the exploitation engendered by slavery. Equality says that it is unfair because people living now should not be held responsible for actions taken before they were born, and is ineffective because it will distort the operations of the free market, disincentivising poor countries from improving their economic situation by working harder and smarter.
This house would make it compulsory for 50% of places on university STEM courses to be offered to women.
Equity says that this is necessary to correct systemic sexism. Equality says that it will unfairly exclude well qualified men and ineffectively include underqualified women; also, that it diminishes the women who are offered places merely because of the quota (the problem of the so-called 'diversity hire').
This house would replace progressive income tax [where higher earners pay a higher percentage of their income in tax] with a flat tax [where everyone pays the same percentage of their income in tax].
Equality says it is fairer to treat everyone the same, and more effective not to disincentivise people from earning more; equity says that it is fair that those who have more should pay more, and is more effective as it provides more money for necessary state investment.
It might look, by the way, as if equity tends to favour the left (favouring state intervention to reduce economic inequality and support minorities) while equality tends to favour the right (favouring people's right to make their own personal and economic choices without interference from the state). However, that isn't necessarily the case. Around two hundred years ago, voting in UK elections was restricted to rich men. Those arguing for universal suffrage, where every person is allowed to vote, did so on the basis of equality, that everyone should be treated the same. Restricting the franchise (that is, who is allowed to vote) was defended on the grounds of equity: it's only fair that women and people who don't own property shouldn't be allowed to vote, as they don't have any significant economic stake in the country. Why should they be allowed to make decisions about something in which they are not involved, and in which they have no expertise? Even today, the franchise is not universal; people under the age of 18 are excluded. A debate on lowering the voting age could split on equality vs equity. Equality would argue that children are as affected by the government's decisions as everyone else, so they should be allowed to have a say in them; equity would argue that it is unfair that people (children) who don't work or pay taxes, or have any experience of adult life, should have the power to influence government decisions.
Once you start thinking in terms of equality and equity, it changes the way you see almost everything.