Agreement with percentages (il 30% sono...)

Analyzing Survey Results

Before diving into statistics, let's look at some vocabulary you will need to discuss surveys and research data:

We interviewed the students with a long questionnaire.
Abbiamo intervistato gli studenti con un lungo questionario.
The doctors have detected a significant result.
I medici hanno rilevato un risultato significativo.

Agreement by Sense

In standard grammar, a singular subject takes a singular verb. But statistics can bend the rules. When a singular percentage (like il venti per cento or il 30%) is followed by di plus a plural noun (like degli intervistati), Italian often uses a plural verb.

This is called concordanza a senso (agreement by sense) — the verb agrees with the plural group of people or things actually performing the action, rather than the singular math term.

Twenty percent of the respondents have finished the questionnaire.
Il venti per cento degli intervistati hanno finito il questionario.
The proportion is dropping, in fact ten percent of the clients are absent.
La proporzione cala, infatti il dieci per cento dei clienti sono assenti.
Forty percent of the respondents in this age bracket have detected the mistake.
Il quaranta per cento degli intervistati in questa fascia d'età hanno rilevato lo sbaglio.

Fractions and Past Participles

This flexible agreement also applies to singular fractions like la metà (half). When "half" refers to a plural group, the verb becomes plural.

Furthermore, if the verb is in a compound tense that requires past participle agreement (such as a passive verb, a reflexive verb, or an essere auxiliary), the past participle must agree in gender and number with the plural noun. It completely ignores the singular percentage or fraction:

Half of the participants had to register in the overall bracket.
La metà dei partecipanti si sono dovuti iscrivere nella fascia complessiva.
30% of the sales dropped.
Il 30% delle vendite sono calate.