ex-ante
Ex Ante means looking at a plan or a forecast before the event happens, based on what you expect rather than what actually occurred.
In plain English
The night before her son's wedding in Owerri, Mama Ngozi sat with her notebook and worked out how much the party would cost. Fifty cows, no, let us say ten cows, three hundred plates of jollof, a band from Enugu, and enough drinks to drown any argument between the two families. She wrote a figure, ₦4,000,000, and told her husband that was the budget.
That figure, the one she calculated before a single pot was cooked or a single chair was rented, is what economists call ex ante. It is a before the fact number. It rests on assumptions, on hope, on past experience of how much rice costs and how many people tend to show up uninvited to a Nigerian wedding.
Ex ante shows up everywhere in economics because so much of planning is guesswork dressed in numbers. A central bank sets an interest rate based on ex ante inflation, meaning the inflation it expects to see in the coming months, not the inflation that has already happened. A business in Lagos draws up an ex ante sales forecast for the Christmas season before December arrives, using last year's pattern and this year's mood.
In the United Kingdom, the Bank of England publishes ex ante growth projections every quarter, telling the public what it thinks the economy will do, well aware that the real, after the fact number, called ex post, often refuses to cooperate.
A Nigerian in Manchester sending money home might do the same thing in miniature. She calculates ex ante that ₦150,000 will cover her mother's hospital bill and the school fees for her nephew. Whether that plan survives contact with the actual invoices is a different story entirely, and that difference is the whole reason economists bother separating the two words.
Mama Ngozi's wedding, in the end, cost ₦5,200,000. The gap between her ₦4,000,000 plan and that final figure is the gap between ex ante and ex post, and it is a gap every Nigerian household budget has met at least once.
A trader in Onitsha expects to sell 200 bags of rice this December and plans her orders around that ex ante figure of ₦6,000,000 in revenue. Come January, she counts her actual sales, the ex post figure, and finds she sold only 150 bags, worth ₦4,500,000.
Questions people ask
What is the difference between ex ante and ex post?
Ex ante is a value based on expectations before something happens, while ex post is the actual value measured after it has happened. Budgets, forecasts and projected inflation are ex ante, while final accounts and actual inflation figures are ex post.
Why does ex ante matter if the real numbers always turn out different?
Because decisions have to be made before the future arrives. A central bank cannot wait for inflation to happen before setting rates, and a business cannot wait for December sales before ordering stock, so ex ante estimates guide action even though they are rarely perfectly accurate.
Where might an ordinary person meet the term ex ante outside of textbooks?
In household budgeting, insurance pricing, government revenue projections before a national budget is passed, and any news report about what analysts expect the economy to do, since all of these are ex ante figures waiting to be tested against reality.
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