On quant careers I: it's a small world
I sometimes see people ask a question along the lines of “should I be a quant or a software engineer” - this to me is a bit like asking “should I be a classical pianist or a manager” - both the industry sizes, selectivity and the diversity of opportunities within each are simply incomparable.
There are on the order of ~20000 quants in the US. Biggest banks have ~<1000, so maybe 10K (=10000) total, biggest 1000+ employees funds and multistrat hedge funds have ~100 quants each. A lot of these 20K are risk and other back-office like roles most people considering the career don’t even think about. Actual “front office” part of the market is more like a few thousand roles at best. Compare this to tens of thousands software engineers at Google alone, and millions in the US.
There is also a difference in selectivity: “front office” quant roles appear to be somewhat more selective than FAANG, and top firms’ directly trading related quant roles might be the most selective generic positions out there. This sometimes leads to dubious fallacies like: “average quant gets paid more than average software engineer so it’s better to be a quant” - wrong! this is not selectivity-adjusted! Or: “being a quant trader at Jane Street is the best role possible” - well, if you’re looking only for things that have a neat “apply” button posted on the internet then maybe so, but the truly best things are just not like that.
Exacerbating the small size of the quant industry is the degree of fragmentation: “quant” is really a catch-all term for a wide range of often very different roles. In a bank one might mostly (on top of coding) use stochastic analysis and niche numerical methods to work on pricing. That is not really needed for most other quant roles. Modeling knowledge and even numerics are often specific to an asset class: if you got your first role in “equity vol” chances are you’re gonna continue there through your career. Stuff learned at banks and other non-systematic roles, usually pertaining to complex instruments requiring modeling, is completely different from statistics/ML/big data needed for roles in systematic funds usually trading simplest instruments.
Quant career is such a narrow and competitive niche that by pursuing it one sacrifices a lot of flexibility. Geography, with most people having to go NYC/Chicago/London/HK, is the obvious one, but not the most important one. More important are very limited choices especially once you’re experienced: if you’re an exotics modeler or rates alpha researcher, there are likely just a few shops in the world you’d consider working at. If you don’t like the boss at one and crazy hours at the other - tough luck. Small size of the field and the fragmentation means for universe of good fits is so small you won’t be able to select for team fit or boss personality or working from home policies or firm culture or hours or anything else on top of that basic fit.
Related is the fact that quant job is a “leaf node”: for many types of quant roles there is very little room for advancement. Banks are actually better at this as the quant orgs at the biggest ones can be as big as ~1K people, and headed by somebody with a quant background. Alpha researchers might transition to PMs, doing similar work with more help and bigger cut. But for most non-bank quants being a head of a small group of quants is the single step up they can realistically hope for in their quant career, and even that is far from certain as ex-bank quant orgs are quite lean and quite flat. Finance as a whole is a large industry, but for most quant-hiring orgs (banks, non-systematic parts of multi-strats, many prop shops) the quants play support rather than core business role (which is played by traders/bankers/portfolio managers), and are usually not in line to make it into core business role or top leadership. Pure systematic places are an exception, being much more of a by quants for quants, but that’s a yet narrower niche still.