Question: In which fields do mathematicians have most job opportunities?

Daniel Bearup answered on 17 Jun 2020:

That depends what you mean by “mathematicians”. If you mean people who studied maths at university and want to use it in their job … well the possibilities are endless. The obvious answer is “financial jobs” but that ranges from classical accountancy (keeping track of a business’s money); to market analysis (working out what is doing well in a “market” – which is itself a broad term); to programming computers to do financial tasks. (In practice, there is no way that I could list all the individual “financial jobs” that exist.)

Engineering is another big area. To some extent it is beneficial to do a specialist degree (Engineering) if you want to get into that … . Engineering is, in large part, about applying maths to a practical problem and will typically teach you about the practical problems and the maths you need to deal with those problems.
On the other hand, in developing fields: e.g. traffic modelling, environment modelling, agricultural modelling, conservation modelling, it may be better to do a general maths course. In these areas, it’s less clear what the problems are/what you need to be able to do, so you need to be flexible. A maths degree is going to give you a much broader (and thus more flexible) tool set which you can apply to any problem, rather than being focused on a particular set of applications.