Hi there! 

To some extent, hiring and firing depends on how many projects MBB has, which is not directly related to the economic climate. For example, a recession can also mean an increase in turnaround work. 

In case they really face issues with their business, first, they will reduce new hires, which is preferable to let people go, as it impacts company more. Also, promotions may be harder to get, and this means people will automatically leave in an up or out system.

Second, how much people will be fired also depends on how fast the company expects business to pick back up, as the hiring and training of new people is expensive and takes time.

While EMs and APs, cost more, these grades already hold more valuable client relationships and expertise, and are harder to replace, so I doubt they will let go first.

So in summary, hiring/firing is not in a 1:1 relationship with business prospects, but with a stiffer economic climate, a career at MBB certainly won't become easier. In the end it depends on your situation: if you perform and bring in business, you won't be let go.

Best,
Adrian