how much and what type of math do you need to know for economics?

At a basic level, as a student of economics, you need to be able to read and interpret graphs, charts, tables and equations. This includes working with spreadsheets, chart-drawing software, finding good-fit equations through a scatter of points, and measures of average such as the mean, the median and the modal value of a set of date.

As a practical economist working in a bank or an insurance company or a government department, you will need to know about probability and making forecasts. This involves number theory, stochastic arithmetic, sample theory, forecasting and prediction, risk analysis and contingency policies [for when things go wrong!]

These are not very difficult but, to be frank, not often taught well in schools or universities. You may need your mathematics to be updated and upgraded; unless you did a mathematical-economics course in the first place.

In the academic world, and in real-life economic consultancy, the demands are greater. All of calculus is essential, plus statistics, plus chart-graphical theory, plus major aspects of model-building which can be very much like theoretical physics or engineering.

So it depends where you plan to do your economics and at which level.

It depends on what exactly you have in mind when you say "economics." Do you mean working as an economist, studying economics, doing research in economics? Once you have an answer to that question, you have to specify the field concerned -- mathematical economics, econometrics, labor economics, health economics, macroeconomic fluctuations, growth theory, etc.

However, instead of just asking questions, I'll give you examples. If we are talking about a professional economist versus an academic economist or a student, less mathematics is required. In fact, besides brief explanations in technical reports that explained how you built your dataset, virtually no mathematics are involved -- and most of it is performed by a computer program. A typicaly economic analysis writen by professional economists is filled with simple graphics, tables and consists mostly in a literary argument. To be fair, though, they do use the knowledge they acquired at college -- it's just implicit because their job is to advise decision maker.

In the academia, either as a researcher or a student, there are some mathematics involved. At the undergraduate level, the most advanced thing you will encounter will likely be matrix calculus because it's convenient -- unless you take pure mathematics courses. I had to use it once in an advanced course (financial economics) to derive the minimal variance envelop in the CAPM model for a specific scenario. At the graduate level, you can see some stochastic differential equations (mostly in financial economics courses and, sometimes, macroeconomics) and you will definitely use linear algebra (econometrics is filled with it, for instance). As you get closer to PhD courses, a few notions of topology and measure theory may come in handy, but as a rule of thumb I'd bet most economics professors can't top a mathematician with only a bachelor degree in terms of proficiency and rigor.

Really, the worst you will see would be in pure mathematics courses and you won't need half of it even for most PhD programs. I can get people to look at me weird if I talk about a probability measure or sigma algebras, but if you take a few minutes to see what they mean and how they're used you wouldn't be impressed at all. Nothing in economic theory and econometrics is really complicated. Even the fanciest mathematics we use isn't so fancy!

math econs.