Why is the past tense used in: "if you needed a new employee”?

Question

Good Economics for Hard Times: Better Answers to Our Biggest Problems By Abhijit V. Banerjee, Esther Duflo

In fact, firms in almost every industry tend to be clustered. Suppose you threw darts at random on a map of the United States. You’d find the holes left by the darts to be more or less evenly distributed across the map. But the real map of any given industry looks nothing like that; it looks more as if someone had thrown all the darts in the same place. This is probably in part because of reputation; buyers may be suspicious of a software firm in the middle of the cornfields. It would also be hard to recruit workers if every time you needed a new employee you had to persuade someone to move across the country, rather than just poach one from your neighbor. There are also regulatory reasons: zoning laws often try to concentrate dirty industries in one place and restaurants and bars in another. Finally, people in the same industry often have similar preferences (computer engineers like coffee, financiers show off with expensive bottles of wine). Concentration makes it easier to provide the amenities they like.

Q: Why did the author use "needed" (past tense)? Is it sequence of tense or semantic aspect?

Answer 1

It's a variant of the second conditional: it might be more familiar if you reverse it as "if every time you needed a new employee etc, it would be hard to recruit workers"

Answer 2

I agree, this is an example of the second conditional, which is used to imagine present or future situations that are impossible or unlikely (eg: If we had a garden, we could have a cat.)

The structure is usually: if + past simple ... modal verb (would) + infinitive

The sentence, "It would also be hard to recruit workers if every time you needed a new employee you had to persuade someone to move across the country" means it is impossible or unlikely to persuade people to move across the country. The sentence is complicated by the fact that needing employees is not at all unlikely, only the act of persuading them to move is. However, since the act of persuading needs to be in the past tense, for verb tense consistency "needed" reads better to me.