post doc

[jackip]

is post doc after getting PhD compulsory?

No. Though this may depend on subject. (DS has just completed a PhD and went through the job market in economics.)

Jobs in academia can be extremely competitive. If you don’t land one straight after a PhD the alternative is often a postdoc. My understanding is that Economics is a relatively high demand subject. DS has a couple of friends who had studied maths, where PostDocs seem more common.

Different subjects have different traditions.

As @Needmoresleep says, taking a PD in Maths has been typical for decades now, at least if you wanted a research intensive career pathway. In Computer Science this has become typical for a research intensive pathway much more recently. In Physics and Chemistry it is an older tradition than in Maths. Etc

Necessary for what? Is the question

For an academic career? Depends on the field. DH did ten years of postdocs and fellowships before getting a permanent post screw he's a high flyer (science). In my field (business school) we often recruit into permanent posts direct from PhD. You should post on the Academic Common Room board.

Sorry, I realise @Needmoresleep did not quite indicate that the Maths tradition is long established. It is

Necessary for what? An academic career - yes unless you are very lucky and find a teaching only job.
Generally - no.
I didn't do a postdoc after my PhD because I didn't want to stay in academia, I got a job in industry instead.
About 50% of people I did my PhD with did a postdoc after for a varying amount of time.
By now only about 10% have stayed in academia and become professors etc

It's generally not necessary, and may not be an advantage if you want a job in industry after your PhD.

What field are you in? I'm a 50 year old half way through a part time English literature PhD. I enjoy it, however do think my chances of getting an academic job afterwards are slim, particularly because I'm in the humanities, can't move for work because I own a home and have a child and because I would like something part time when I finish at 53.

Typically... if you want to stay in academia, then yes. They're a way to boost the numbers of papers you have, which is key to getting associate and professor roles.

If you're going into industry, no.

Because I don't know much other than observe DS making 240+ applications, with fly out interviews on 4 continents.

Roughly a third of his peers got research intensive posts, a couple with big name institutions, a third got post docs and a third went to work for research consultancies. My understanding is that economics is lucky in that there is plenty of research carried out by the private sector. I also understand that there is advantage in taking a PostDoc as it gives you a chance to get started on research before taking a permanent job and the accompanying pressure to publish.

The challenge will be the need for world wide mobility during the early years of a career. I don't know if the same is true in other subjects.

Mobility is often required. One of my postdocs is on a highly competitive EU fellowship where mobility is a condition of the grant. Others not so much eg Leverhulme.

Marie Curie? DH had one of those and had 2 years in the US. Really tough for us at the time, but allowed him to get a permanent job in his "home" institution so we could properly settle down. Worked really well for us in the long term and actually we both have some really lovely memories of that time.

I assume the question is 'is a postdoc necessary to get a permanent academic job'. Clearly it's not necessary for any other career.

Getting a permanent job in academia involves a huge bottleneck and only a small minority of PhD-holders will achieve it. In this context, a postdoc is massively desirable - I wouldn't frame it as something 'necessary', more as 'something you'd give your eye teeth to get', given the other option straight out of your PhD is probably a short term (often quite exploitative and poorly paid) teaching-only position. Post-docs give you the chance to build your own research profile and publication record, and so make you competitive relative to other candidates.

I assume the question is 'is a postdoc necessary to get a permanent academic job'. Clearly it's not necessary for any other career.

It may not be so clear to PhD students - it may appear to them, from within the academic environment, that a postdoc will be bound to put them ahead in employability in industry. In some niche fields it may, but the thing to definitely avoid is becoming a 'perpetual post doc'