<p>Fifty percent of the people alive today (have) never made a phone call, (but) thirty percent (still) have no electricity connections to (their) homes. No error.</p>
<p>I thought “have” and “their” are wrong because they should be singular, since the subject refers to a quantity/amount and answers the question “how much?”. We say: “twenty percent of the class is going to fail the test”. So, “have” should be “has”, and “their” should be “its”???</p>
<p>The answer is “but”, because it makes an illogical transition between the clauses. </p>
<p>Are all three wrong? Or can phrases referring to measurement, quantity/amount be flexible like collective nouns, meaning you can use the plural form and the singular form? For collective nouns, it depends on how you refer to them—as discrete entities or as a single unit.</p>
<p>Thanks in advance.</p>