further I would say that over the last time companies also tend to introduce additional internal chierarchies which are not always visible to extern.
In order to keep promotion cycles relatively short (12-18 months) companies have started to split existing career levels into informal 1 & 2 sublevels.
I can give you an example how this logic was applied at Roland Berger, but I know that other tier-1 also started to look at this approach.
Previous and current career grades:
Junior Consultant Assistent (Intern) -> Junior Consultant Assistent (Intern) and Masterand (intern in Master's semi final year); The company has started to differentiate the pay for bachelor's and master's intern, while in general significantly increased the salary for interns;
Business/Consulting Analyst -> Business/Consulting Analyst 1 and Business/Consulting Analyst 2. This is an entry position for bachelor graduates. A quick promotion from 1 to 2 is possible after 6 or 12 months depending on your development speed.
Junior Consultant -> Junior Consultant 1 and Junior Consultant 2. This is an entry position for master graduates. A quick promotion from 1 to 2 is possible after 6 or 12 months depending on your development speed.
Consultant -> Consultant 1 and Consultant 2. This is an entry position for PhDs or young professionals with up to 3 years of experience. A quick promotion from 1 to 2 is possible after 6, 12 or 18 months depending on your development speed.
Senior Consultant -> Senior Consultant 1 and Senior Consultant 2. This could also an entry position for PhDs or young professionals with 3-5 years of experience, if they performed very well during the interview. A promotion cycle between 1 and 2 could be 12, 18 or 24 months depending on your development speed. Normally it takes 4-6 years to get from the junior position to the Project Manager (PM) depending on your performance and luck.
Project Manager -> PM 1 and PM 2. Promotion between 12 and 24 months depending on performance. It usually takes another 12-36 months to be promoted from PM2 to Principle depending on your ability to sell projects and sell yourself in front of the partners.
Principle - is the only career level which has not yet been splitted furhter. You need to reach minimum turnover in order to be promoted to the Partner level.
Partner -> P1, P2 and P3. Even on the Partner level there is a huge differentiation. Partner P1 is a newly promoted partner who sells projects for less than 4m Euro/USD. Senior Partner P2 is a more experienced colleague, who is able to sell annually more than 4m Euro/USD. Senior Partner P3 is either a Regional Director or Member of the Management or Supervisory board of the company.
Even though this logic comes from RB, it also applies to McKinsey and other MBB/Tier-1 companies. They only call the career levels differently.
Hope it brings you furhter clarity.