Uneven hiring in corporations?

I'm trailing with hi-tech engineers so a number of corporations can't hire 100%.

What I wonder is why the increase in their hiring isn't even?

For example I have two exactly identical electric power companies, but one has hiring level 90 and the other only 70!?!? (salaries are identical, they have all raw materials and every product is being sold).

I've never worked that one out myself. Just know it does happen, it's not just you. Maybe it's assets or market value or cash or something.

One trick I've used is to set one corp, like a not so good one, at salary of 30 and then only that one should be short unless you are down lots of workers. In fact my 30 salary wine corp now makes a good a profit as any. And doing that can help your govt. costs quite a bit too, but thats another story.

PS, you must get your hiring to 100% pronto, for all corps.