A woman gives birth in the UK every 48 seconds. She must be exhausted.
Which reminded me of a recent conversation I had about the surprisingly dangerous skills of deer:
Every year, somebody's dog gets killed by a deer. It's always the same person. They never learn. You just shouldn't have a Chihuahua in Churchill, Manitoba
Let's go for a slightly simpler sentence to see the two readings:
Everyone loves someone.
This has two possible readings:
1. For all people, each person has some person that they love (but it might not be the same one).
2. There is some particular person who everyone loves.
In the first reading, we interpret the "every" as having scope over over the "some" (for every...there is some...) while in the second reading, we interpret the "some" as having scope over the "every" (there is some...who every...). Or in more simplified notation:
1. EVERY > SOME
2. SOME > EVERY
Back to the original sentences, which also have the same two readings. I'm going to paraphrase them to make it more obvious.
Some woman gives birth every 48 seconds.
1. EVERY > SOME: For every period of 48 seconds, there is some woman who gives birth (not necessarily the same one).
2. SOME > EVERY: For some particular woman, she gives birth every 48 seconds.
Every year, some dog gets killed by a deer.
1. EVERY > SOME: In every year, there is some dog who gets killed by a deer (not necessarily the same one).
2. SOME > EVERY: For some particular dog, it gets killed every year.
However, notice that it doesn't matter what the linear order is between them: in the giving-birth example, SOME comes before EVERY, while in the deer example, EVERY comes before SOME. But in both cases, both readings are available (one of them is a highly implausible scenario in real life, but that's where the humour comes from).
Words like "every" and "some" (also a/an, each, a few, all, etc.) are known as quantifiers, and this phenomenon as a whole is known as quantifier scope ambiguity (or more generally just scopal ambiguity) and has gotten quite a lot of attention in semantics. A full explanation of the various proposals is beyond the scope (hm) of this post, but one popular approach is covert quantifier raising.
