Which form of punctuation is correct for whereas?

Question

I've read in grammar books that "whereas" is a kind of conjunctive adverb and should be placed at the first of a sentence or else it have to be followed by a semicolon. But I've seen in many books that they just put a comma before it, so I am a little bit confused.

For instance look at the following examples:

1. Back in the day, people would frequently go out to meet friends, whereas today they prefer to stay at home alone, chatting online.

2. The number of people who use smart phones is increasing; whereas, the proportion of people go out for leisure activity is decreasing.

From grammar books, I feel like the second form is correct, but I have seen the first form of punctuation as well.

Answer 1

Your first example is certainly far more common usage than the second. It is quite rare to need punctuation both before and after a single word, and that is not one of them.

Indeed, I cannot think of any example in common, modern usage where a semi-colon would come directly after "whereas" - that word is mainly used to join two phrases, whereas a semi-colon is used to separate them.