Addeetional Member Seestem
The Addeitional Member Seestem (AMS) is a votin seestem whaur some representatives is waled frae geographic constituencies an ithers is waled bi proportional representation frae pairty leets. The constituency representatives is for normal waled unner the first-past-the-post votin seestem. The pairty leet representatives is waled bi a saicont vote, whaur the electors vote for a political pairty, no directly for onie ae chiel. This pairty vote determines the nummer o representatives that the pairty haes in the assembly. The parteicular individuals waled comes frae leets drawn up bi the political pairties afore the walin, at a naitional or regional level.
Variations o the AMS haes unalike weys o determinin hou monie pairty leet representatives ilka pairty is enteitelt tae. The chief differ atween seestems is whither the constituency representatives is coontit whan leet representatives is allocate tae ilka pairty.
- Unner the Mixt Member Proportional (MMP) or Tap-up seestem, the ettle is for the pairty's tot o representatives, includin constituency representatives, tae be proportional tae its percentage o the pairty vote.
- Unner the parallel votin or Supplementary Member (SUP) seestem, the pairty leet saets is allocate proportionally, an onie constituency saets the pairty micht hae wan is eikit on.
Parallel votin is the mair common variation amang votin seestems o the warld, but MMP is the seestem descreived here. Smaa pairties will for ordinar wun mair saets unner MMP nor SUP.
Table o contents
The AMS is uised tae wale members tae sindry representative bodies aroond the warld.
- New Zealand, whaur the seestem is kent as MMP (Mixt Member Proportional) juist, no as AMS
- Unitit Kinrick
It wad hae been uised for the proponed Regional Assemblies in England an aa.
Recommends for Breitish walins 
In 1976, the Hansard Society recommendit that the Addeitional Member Seestem shuid be uised for UK pairlamentary walins, but insteid o uisin closed pairty leets, it propones that saets shuid be filled bi defeatit candidates, on a 'best losser' basis. A seimilar seestem wis proponed bi the Unthirlt Commission in 1999, kent as Alternative Vote Plus (AV+). This wad involve the uise o the Alternative Vote for walin members frae ae-member constituencies, an regional pairty leets. Houaniver, contrair tae the Labour Pairty's aerlier manifesto promises, the wisna a referendum afore the 2001 walin and the statement wisna repeatit.
The voter casts twa votes: ane for a constituency representative an ane for a pairty. In a lesser-uised variant, uised bi some of the sindry Länder in Germany, baith votes is combined intae wan, sae that votin for a representative autaematically means votin for thair pairty an aa.
On the district or naitional level (i.e. abuin the constituency level), the hail nummer o saets in the assembly is allocate tae pairties proportional tae the nummer o votes the pairty got in the pairty portion o the ballot. The nummer of constituency saets a pairty wan is subtractit frae its allocation. The nummer o saets bydin allocate tae that pairty is filled uisin the pairty's leet. If a candidate is on the pairty leet, but wuns a constituency saet, thay dinna get twa saets; insteid, thay are delete frae the pairty leet an replaced wi the neist candidate doun.
Owerhang saets 
Acause a pairty can gain less saets bi the pairty vote nor thay need tae justifee the constituency saets thay wan, owerhang saets can come aboot. The'r different wey o dealin wi owerhang saets. In the Scots Pairlament the nummer o owerhang saets is taen frae the nummer o proportional saets o the ither pairties, in Germany's Bundestag an the New Zealand Hoose o Representatives the owerhang saets bydes. In some seestems the ither pairties receive mair saets tae restore proportionality.
For tae be eligible for leet saets in the New Zealand an German, a pairty maun either earn at laest 5% o the hail pairty vote or wun at laest ane constituency saet (three constituency saets in Germany). If nane o the twa condeitions is met, the pairty isna representit. Haein a member wi a 'sauf' constituency saet is syne a grand asset tae a minor pairty in sic a seestem.
Potential for tactical votin 
In terms o tactical votin, the first vote for the district representative is aften muckle less important (nor the saicont pairty leet vote) in determinin the oweraa ootcome o a walin; in ither cases a pairty micht be sae siccar that it'll wun saets in the district walin that it expects nae mair saets in the proportional tap-up. Some voters micht syne ettle tae get dooble representation bi votin tactically an splittin thair votes, tho this rins the risk o unintendit eftercomes.
In seestems wi a thrashel, tactical votin for a minor pairty that's predictit tae be juist ablo the thrashel is relatively common, specially bi voters that's feart that the minor pairty missin the thrashel wad weaken the lairger political camp that the minor party belangs. For exemplar, the German moderate-richt Free Democratic Pairty (FDP) haes aften received votes frae voters that wad liefer the lairger Christian Democratic Union (CDU) pairty, acause thay fear that gin the FDP received less nor five percent o the votes, the conservative camp wad be sic weakened that the CDU cuidna form a guvrenment.
Political pairties can abuise the seestem: in the 2001 Italian walins, the twa chief coalitions (the Hoose o Freedoms an the Olive Tree) linkit monie o thair constituency candidates tae wyle-leets (liste civetta) in the proportional pairts, uner the names Abolizione Scorporo an Paese Nuovo respectively, sae that gin thay wun constituencies than thay wadna reduce the nummer o proportional saets received bi the coalitions. Atween thaim, the twa wyle-leets wan 360 o the 475 constituency saets, mair nor hauf o the 630 tot o saets, mauger wunnin a tot aathegither o less nor 0.2% o the naitional proportional pairt o the vote. In the case o Forza Italia (pairt o the Hoose o Freedoms), the tactic wis that successfu that it didna hae eneuch candidates in the proportional pairt tae receive as monie saets as it in fact wan, missin oot on 12 saets.
Wyle-leets isna uised in maist kintras uisin AMS, whaur maist voters vote for candidates frae pairties wi lang-staundin names.