Important Notice: New Electoral Systems for the Senate and the Chamber of Deputies

In December 2005, Italy adopted bonus-adjusted proportional representation electoral systems for elections to the Senate and the Chamber of Deputies; in turn, these were replaced by new, mixed electoral systems introduced in October 2017. This page describes the system previously used for the 1994, 1996 and 2001 elections to the Senate, which nonetheless was retained for the region of Trentino-Alto Adige until 2017.

An overview of the Senate electoral system introduced in 2005 is presented here.

The Italian Senate is composed of 315 elected members. A total of 232 seats are filled in single-member constituencies or colleges (collegi); the remaining 83 seats are distributed by proportional representation (PR). Senate seats are apportioned among Italy's twenty regions in proportion to their population; nonetheless, each region is guaranteed a minimum of seven seats, except Valle d'Aosta, which elects one senator, and Molise, which elects two. Approximately three-quarters of the senators in each region are elected in single-member colleges; PR is used to choose the remaining one-quarter, except in Valle d'Aosta and Molise, where all the seats are filled in single-member constituencies. In Trentino Alto Adige, with seven Senate seats, only one senator is elected by PR; the region has six college seats - three in Italian-speaking Trento (Trent) province, and three in German-speaking Bolzano (Südtirol) province.

For the 2001 Senate election, the regional distribution of seats was as follows:

Beginning with the next parliamentary election, due in 2006, Italian citizens residing abroad will elect six senators, and the number of seats apportioned among the regions will decrease to 309.

Since 1993, Senate single-member colleges are filled by the plurality or first-past-the-post method, under which the candidate obtaining the largest number of votes in each college is elected. Previously, from 1948 to 1992, a majority of at least sixty-five percent of the valid vote was required for election to a Senate single-member constituency; otherwise, no candidate was elected to fill the seat, which was added to the regional PR pool, where it was allocated.

The proportional seats, allocated at the regional level, are distributed according to the number of votes obtained by each group, excluding votes won by candidates elected to a college seat. The apportionment is carried out by means of the largest average method of PR, conceived by the Belgian mathematician Victor d'Hondt in 1899. Within each group, proportional mandates are awarded to defeated candidates with the highest vote percentages, relative to other candidates from the same group.

A single election ballot is used to fill both constituency and proportional seats. There is no statutory threshold for participation in the regional allocation of Senate proportional seats; however, the application of the d'Hondt rule introduces a de facto threshold at the regional level.

To illustrate the functioning of the system, the allocation of seats in the Emilia Romagna region for the May, 2001 general election is presented here in detail. At the time, the region had fifteen college seats and six proportional seats, for a total of twenty-one seats. Six groups contested the Senate election in the region, namely L'Ulivo (The Olive Tree); the Casa delle Libertà (House of Freedoms); Rifondazione Comunista (the Communist Refoundation Party); the Lista Di Pietro (Di Pietro List); the Pannella-Bonino List; and Democrazia Europea (European Democracy).

The first step was the allocation of the fifteen single-member college seats, detailed below:

College seats were awarded to the group obtaining the largest number of votes in each constituency (shown in bold italic). As indicated, the Olive Tree coalition won fourteen college seats, while the House of Freedoms cartel won one college seat; the remaining groups won no constituency seats.

It becomes immediately evident that the distribution of college seats in the region was far from proportional: on the contrary, the first-past-the-post system greatly amplified the Olive Tree's large popular vote majority, as the coalition secured fourteen out of fifteen constituency seats, or 93.3% of the total, with just 52.0% of the vote. Meanwhile, the House of Freedoms, with 35.5% of the vote, won just one college seat, or 6.7% of the total. As for the other groups, all of them were trailing far behind the two major groups with single-digit percentage scores across the region, so it was hardly surprising that all failed to win even a single constituency seat.

This is not an unusual outcome: the first-past-the-post system usually favors the major groups, particularly the majority ticket, which often receives a share of seats well above its proportion of the popular vote, at the expense of its opponents - which was exactly the case here. At the same time, it severely handicaps minor parties with evenly spread support, which practically have no chance of winning any seats - which was also the case in this situation.

The next step was the calculation of each group's electoral total (cifra elettorale), in order to distribute the proportional mandates at the regional level. To that end, the votes obtained by each group's winning candidates were deducted from its corresponding regional vote total. The deductions, known in Italian as scorporo (that is, subtraction), and the electoral totals for each group are detailed below.

Note that the electoral total for each group is equivalent to the aggregate number of votes obtained by the group's defeated college seat candidates.

The electoral total polled by each group was then divided by 1, 2, 3, and so on until the number of seats to be allocated was reached, as detailed below:

Seats were then awarded to the groups obtaining the largest quotients or averages (shown in bold). As indicated, the House of Freedoms won five seats, while the Communist Refoundation Party secured one seat.

The apportionment of constituency seats can also be obtained by dividing the electoral total for each group by the smallest quotient used to allocate seats, disregarding the remainders. For the election in Emilia Romagna, the electoral total obtained by each group would be divided by the sixth largest average - 151,892 votes - with the following results:

The smallest quotient used to allocate proportional seats is also the effective representation threshold, which is the number of votes necessary to secure one seat. For the Emilia Romagna region, this threshold amounted to 5.6% of the vote.

The seats won by each group were awarded to its defeated college candidates with the highest vote percentages, relative to other group candidates. In this manner, the defeated Casa delle Libertà candidates in Colleges 2, 4, 6, 13 and 15 were declared elected at the regional level, as was the defeated Rifondazione Comunista candidate in College 12.

As such, the results of the Senate election in Emilia Romagna were as follows:

Once again, seats awarded at the college level by simple majority are shown in bold italic, while seats allocated at the regional level by proportional representation are shown in italic.

The definitive seat distribution in Emilia Romagna was not fully proportional: it still favored the largest group in the region, although in a less overwhelming manner than the initial first-past-the-post seat distribution. At the same time, the allocation of proportional mandates allowed the larger minority groups in the region to attain a level of representation closer to their popular vote strength.

Clearly, the allocation of PR mandates helps parties that have won few or no constituency seats. However, the largest average method has a tendency to favor the major groups - the subtraction of votes cast for college seat winners notwithstanding - which intensifies as the number of proportional seats decreases. This tendency is compounded by the cumulative effect of the application of the d'Hondt rule over a small number of proportional mandates, spread across eighteen regions: on average, each of these returns five proportional seats. Consequently, in most regions the effective representation threshold constitutes a significant barrier for participation in the regional allocation of proportional mandates.

For the 2001 Senate election, the regional allocation of proportional seats by the largest average method produced the following effective thresholds:

Since the effective representation threshold, as a percentage of the total vote, increases as the number of proportional seats decreases, minor parties with evenly spread support usually have very little chance of winning any seats.

However, it should be stressed that while proportional representation has some influence over the composition of the Senate, elections to the upper house of the Italian legislature are now largely decided in the single-member colleges, filled by the first-past-the-post method.

The functioning in practice of the Senate electoral system is illustrated by the outcome of the May, 2001 election:

The House of Freedoms was the main beneficiary of the first-past-the-post election system, with 152 out of 232 college seats (65.5%), on a 42.5% share of the vote. Meanwhile, none of the minor parties secured representation at the college level, with the exception of the Vallée d'Aoste ticket, which contested the election solely in Valle d'Aosta, and the Südtiroler Volkspartei (South Tyrolean People's Party), which fielded candidates only in the German-speaking areas of Trentino Alto Adige. Despite having a tiny electoral following on a nationwide scale, the votes obtained by these two tickets were strongly concentrated in specific geographic areas: as a result, both achieved representation slightly above their respective proportions of the popular vote.

The Olive Tree managed to recover some ground in the proportional allocation of regional seats, which allowed the coalition to secure a share of seats slightly above its proportion of the popular vote. Some proportional seats were awarded to minor parties which had won no constituency seats, but the House of Freedoms won a significant number of proportional mandates - mainly in central Italy's so-called "red belt", where the Olive Tree won most of the college seats - thus retaining a sizable (if reduced) Senate majority.

It is worth noting that the introduction of plurality voting in single-member constituencies has profoundly affected the manner in which political parties contest parliamentary elections in Italy. Since the persistently fractious nature of the country's multi-party political system makes it very difficult for any single party to secure an absolute majority of seats in either house of Parliament solely on the account of its own electoral following, Senate and Chamber of Deputies elections held under the new system have been dominated by electoral coalitions, formed by diverse political parties of similar (and sometimes less than similar) ideological persuasions. Under the single-ballot Senate system, these coalitions also participate directly in the proportional distribution of regional mandates. However, the Chamber of Deputies electoral system provides for separate constituency and proportional election ballots, which allow political parties within a coalition to run independently for the distribution of lower house proportional seats.

Copyright © 2003-2018 Manuel Álvarez-Rivera. All Rights Reserved.
Last update: March 4, 2018.