This is indeed very confusing.

Did this sentence appear in the newspaper "The Economist" or did it appear in "Economist GMAT"?

If it appeared in "Economist GMAT", then I would request an expert's response.

Yeah, I think there's a mistake.

I'm pretty sure "which" modifies what's just before the comma, so here it's saying "opportunities leads" thus causing a verb number agreement problem too.

Is my understanding correct?

Outside the GMAT, which + SINGULAR VERB is sometimes used to refer to the ENTIRE PRECEDING CLAUSE.
This usage is NOT PERMISSIBLE on the GMAT.
On the GMAT, which + SINGULAR verb must serve to refer to the NEAREST PRECEDING SINGULAR NOUN.

The following sentence would constitute an INCORRECT ANSWER CHOICE on the GMAT:
Every day, our teams collaborate around the world to actively uncover, discuss and debate investment opportunities, which leads to better decisions for our clients.
Here, which leads (which + SINGULAR VERB) lacks a clear singular antecedent.
While the intent is for which leads to refer to the entire preceding clause, this usage is not permissible on the GMAT.

Thanks Mitch.
If a sentence has noun + prepositional phrase + Which + verb, will Which refer to the noun?

I read a book written by ABC, which was very boring.
In this sentence, "written by ABC" should not block Which from referring to the BOOK.

A classic official example of the NOUN + PREPOSITIONAL PHRASE + WHICH:

"Emily Dickinson's letters to Susan Huntington Dickinson, which were written..."

The verb in the "which" clause is "were," so we know that "which" is plural, and must therefore have a plural antecedent. "Which" must be referring to "letters."

kutlee wrote:Courtesy - Economist

Every day, our teams collaborate around the world to actively uncover, discuss and debate investment opportunities, which leads to better decisions for our clients.

Here what does Which refer to?
Which should refer to nearest noun. But in the above the sentence, which refers to the process of collaboration and discussion.

Hello kutlee,

Sentential Relative Clauses are not allowed on the GMAT. The construction of the sentence you have given has a sentential relative clause modifier, which modifies the entire previous clause. However this is not allowed on the GMAT.

If a sentence has noun + prepositional phrase + Which + verb, will Which refer to the noun?

I read a book written by ABC, which was very boring.
In this sentence, "written by ABC" should not block Which from referring to the BOOK

There are some exceptions to the touch rule:-
1)An absolutely essential modifier falls between e.g noun + prepositional phrase + Which + verb.This construction will be valid.

2)A very short predicate falls between , shifting a very long modifier back.

3)A short non-essential phrase intervenes and is set-off by commas.

4)The modifier is part of a series of parallel modifiers, one of which touches the noun.

So, by rule (2) 'written by ABC' will not block which from referring to the book, since it is a short predicate

Aman verma wrote: There are some exceptions to the touch rule:-
1)An absolutely essential modifier falls between e.g noun + prepositional phrase + Which + verb.This construction will be valid.

2)A very short predicate falls between , shifting a very long modifier back.

3)A short non-essential phrase intervenes and is set-off by commas.

4)The modifier is part of a series of parallel modifiers, one of which touches the noun.

Hello Aman, can you please give examples for each/few of the above exceptions from official GMAT sources, so that we have a better understanding.

Even if you give example of one of the above exception, then hopefully other experts would pitch in with examples of other exceptions (that you have stated above), so that we can have "real examples" for all the exceptions.

DavidG@VeritasPrep wrote:A classic official example of the NOUN + PREPOSITIONAL PHRASE + WHICH:

"Emily Dickinson's letters to Susan Huntington Dickinson, which were written..."

The verb in the "which" clause is "were," so we know that "which" is plural, and must therefore have a plural antecedent. "Which" must be referring to "letters."

Thanks David! That's wild...this was literally the question I was going to ask about this issue.

kutlee wrote:Thanks Mitch.
If a sentence has noun + prepositional phrase + Which + verb, will Which refer to the noun?

On the GMAT:
COMMA + which + SINGULAR verb must refer to the nearest preceding SINGULAR non-person noun.
COMMA + which + PLURAL verb must refer to the nearest preceding PLURAL non-person noun.

As David points out, SC29 in the OG13 abides by this rule:
Emily Dickinson's LETTERS to Susan Huntington Dickinson, which WERE written over a period beginning a few years before Susan's marriage to Emily's brother and ending shortly before Emily's death in 1886, outnumber her letters to anyone else.
Here, which were written (COMMA + which + PLURAL verb) correctly refers to the nearest preceding non-person PLURAL noun (letters).

An incorrect answer choice in GMATPrep:
The company will increase its share of the $21 billion book market in the country, which ranges from obscure textbooks to mass-market paperbacks.
Here, which ranges (COMMA + which + singular verb) seems to refer to country (the nearest preceding non-person singular noun), implying that the COUNTRY ranges from obscure textbooks to mass-market paperbacks.
Not the intended meaning.

I read a book written by ABC, which was very boring.
In this sentence, "written by ABC" should not block Which from referring to the BOOK

Here, since which cannot serve to refer to a person, it seems clear that which was (COMMA + which + singular verb) refers not to ABC (the author) but to a book (the nearest preceding non-person singular noun).