Past continuous passive or Past simple passive

Question

I was recently doing passive voice exercises when I came upon this sentence in "English Grammar in Use Supplementary Exercises", and here is the aforementioned sentence and the content of the task:

"Complete the second sentence so that it has a similar meaning to the first sentence. Do not use by unless it is important to the meaning

During the summer, the cafe was employing more waiters every week.
My version: During the summer, more waiters were being employed every week.
Author's version: During the summer more waiters were employed every week.

Is my version wrong or not? I think there should be past continuous passive because it is a continual period of time.

Answer 1

Yes and no...

During the summer, more waiters were being employed every week.

This would mean as much as stacking the staff over that particular summer; e.g. after four weeks, they reached the number of 20 waiters. In other words, the whole number of waiters is referred to as "a bulk" AND the group would be still open in terms of hiring — we don't know if they stopped hiring.

During the summer more waiters were employed every week.

Here, the gamechanger is every week and the passive voice. The number of waiters is referred to as "chunks." In other words, the author might want to put stress on the fact that the stuff was somehow "capped" every week — week 1: we have 7 waiters, week 2: we have 14 waiters, etc...

As you may see, the difference doesn't take particular importance mostly. I would recommend you remember that adverbial expressions of time that deal with sequences (every week, every so often, every second day, etc.) like simple tenses in the passive form. However, it's not a rule, which I proved above, but rather an examinatorial tendency. I hate that the answer keys to coursebooks do not show a problem in a spectrum.

Acquire COBUILD English Grammar and search for quick tips there. It deals with a ton of problems like this.

Answer 2

It is a matter of choice of emphasis, Cambridge says:

Often there is little difference between the past continuous and the past simple, except that the past continuous suggests that the event(s) were in progress at a time in the past or that they were happening as background or temporary events. Whether we choose to use the past continuous or past simple often depends on how we see the past event(s).

Compare

• Doctors were treating patients in temporary beds and they were trying to do their best in a difficult situation.

(Past continuous: writer chooses to show the events as ongoing at that time in the past.)

• Doctors treated patients in temporary beds and they tried to do their best in a difficult situation.

(Past simple: writer chooses to show the events as finished.)

So in your sentence, it seems the author simply wanted to stress the employment of waiters as a finished action, and as it stands on its own, I think it is a better option.

During the summer more waiters were employed every week.

And it is a better option, because your version would be better off with more context to justify the use of the past continuous. To stress progress at a certain point in time or during a period, it helps the whole statement to connect it to another simultaneous or parallel action in progress:

During the summer, more waiters were being employed every week as the restaurant was attracting more clients.

It is just more plausible to emphasise progress in this way. However, just because it needs more context to make sense, it does not mean it is incorrect.

Here is what Rodney and Pullum says about this

When a clause describes a situation in a way that considers it as a whole, in its totality, without reference to any internal temporal structure or subdivision it might have, we say that the clause has a perfective interpretation. When a clause describes a situation in a way that makes reference to its internal temporal structure or subdivisions, we say that the clause has an imperfective interpretation. The following examples illustrate the distinction :

• PERFECTIVE
  ia. She wrote a novel.
• IMPERFECTIVE
  ib. She was writing a novel.

The natural interpretation of [ia] is perfective: it simply describes an event that took place in the past. Example [ib], by contrast, has an imperfective interpretation : we are not concerned with the total event of her writing a novel, but with just part of it, some part in the middle during the process of its composition. Note that it does not follow from [ib] that she ever actually completed the novel. (English Grammar, p. 42)

A more striking example might help to distinguish the difference:

Several people were injured during the demonstration.

and

Several people were being injured during the demonstration.