Why does the d’Hondt method tend to favor larger political parties?

The d’Hondt method is a largest-average formula used in party-list proportional representation to allocate legislative seats. It tends to favor larger political parties because of how it calculates the divisor for seat distribution.1

Under the d’Hondt method, a party’s vote total is divided by the number of seats it has already been awarded plus one. Because the divisors used are consecutive integers (1, 2, 3, etc.), the mathematical impact of the division is less punitive for parties with high vote totals compared to methods that use larger or odd-numbered divisors, such as the Sainte-Laguë method.1

Consequently, while the system aims for proportionality, it has a slight inherent tendency to overreward larger parties and make it more difficult for smaller parties to secure legislative representation.1