Although very unofficial on the next list over fifty pilots are posted inactive for example retirement, disability etc.
There is a capability to hire over fifty pilots and this is with a reduction on all B-767 First Officer positions and B-767 Relief Pilot positions.
Getting hired is like winning the lottery (without the cash at first) but through time you will advance to what ever position you want to be in that your seniority will allow.
There are two schools of thought in the airline world; one is bid everything to the bottom for the most junior position on the biggest aircraft you can hold. Up side is you get the opportunity to fly the bigger aircraft early. Downside is you are on reserve think of the Maytag repairman short calls, no choice for vacation, not very conducive for home life.
Stay senior on junior rated positions. Up side your choice of working conditions, vacation, days off (never miss your children's birthday parties) down side you do not get on the larger aircraft earlier.
After saying that in your career you will become senior before you know it but enjoy the ride and if you are given lemons make lemonade...