Editing Single transferable vote (section)

===Migration of preferences===
The relative performance of political parties in STV systems is sometimes analysed in a different fashion from that used in other electoral schemes. For example, seeing which candidates are declared elected on first-preference votes alone in the 2012 Scottish local elections, where 1223 members were elected, can be shown as follows:

{| class="wikitable" style="text-align:right;"
|+ [[2012 Scottish local elections]]{{sfn|Curtice|2012|p=22}}
|-
!rowspan="2" colspan="2"|Party !!rowspan="2"|Total elected !!colspan="3"|Elected on 1st prefs alone
|-
!Total!!%!!% (2007)
|-
| {{Party name with colour|Scottish Conservatives}}
| 115|| 46|| 40||41
|-
| {{Party name with colour|Scottish Labour}}
| 394|| 199|| 51||37
|-
| {{Party name with colour|Scottish Liberal Democrats}}
| 71|| 20|| 28||22
|-
| {{Party name with colour|Scottish National Party}}
| 425|| 185|| 44||57
|-
| {{Party name with colour|Scottish Greens}}
| 14|| 1|| 7||–
|-
| {{Party name with colour|Independent politician}}
| 200|| 79|| 40||32
|-
|style="width: 5px; data-sort-value="Other"|
|style="text-align: left;" scope="row"| Other
| 4|| 2|| 50||14
|-
|colspan="2" style="text-align:left;"|'''Totals'''
| 1,223|| 532|| 44||40
|}

The data can also be analysed to find the proportion of voters who express only a single preference,{{sfn|Curtice|2012|p=13}} or those who express a minimum number of preferences,{{sfn|Curtice|2012|p=14}} to assess party strength. Where parties nominate multiple candidates in an electoral district, analysis can also be done to assess their relative strength.{{sfn|Curtice|2012|pp=17–18}}

Other useful information can be found by analysing terminal transfers{{em dash}}i.e., when the votes of a candidate are transferred and no other candidate from that party remains in the count{{sfn|Curtice|2012|p=14}}{{em dash}}especially with respect to the first instance in which that occurs:

{| class="wikitable" style="text-align:right;"
|+ Average first terminal transfer rates (2012){{sfn|Curtice|2012|pp=15–16}}
|-
!rowspan="2" colspan="2"|Transferred from !!rowspan="2"|% non-transferable !!colspan="5"|% transferred to
|-
!Con!!Lab!!LD!!SNP !!Ind/Other
|-
| {{Party name with colour|Scottish Conservatives}}
|34 ||– ||8 ||32||8 ||18
|-
| {{Party name with colour|Scottish Labour}}
|48 ||6||– ||13||17 ||17
|-
| {{Party name with colour|Scottish Liberal Democrats}}
|23 ||22 ||20 ||– ||16 ||19
|-
| {{Party name with colour|Scottish National Party}}
|44 ||6 ||18 ||14 ||– ||18
|-
| {{Party name with colour|Scottish Greens}}
|20 ||5 ||19||20 ||18 ||17
|}

The transfers of votes under STV mean that candidates who did well on first-preference votes in the first count (but not well enough to be immediately declared elected) may not be elected in the end, and those who did poorly on the first count may be elected in the end. This is due to transfers made according to second and later preferences. This can also be analysed, again using the 1223 members elected in the Scottish local elections. Some of the leading candidates in the first count were not elected but, comparing the number to the total number of members elected in these elections, the successful candidates were mostly set in the first count (through the simple mechanics of single voting in multi-member districts), before any vote transfers are done. Only about ten percent or less of the front runners in the first count were not elected in the end.

Only 68 of the elected members, of the overall 1,223 successful candidates, were not already in a winning position in the first count, thus showing that vote transfers merely put a polish on the first-count ranking of candidates established through single voting in multi-seat districts.

{| class="wikitable" style="text-align:right;"
|+ Candidates not in a winning position on 1st preference who secured election, by party (2012){{sfn|Curtice|2012|p=23}}
|-
!rowspan="2" colspan="2" | Political party !! scope="col" rowspan="2"|Elected though not in top 3 or 4 !! scope="col" rowspan="2" | Not elected though in top 3 or 4 !! colspan="2" | Net gain/loss
|-
! 2012 !! 2007
|-
| {{Party name with colour|Scottish Conservatives}}
| 1|| 16|| −15||−24
|-
| {{Party name with colour|Scottish Labour}}
| 21|| 8|| +13||−17
|-
| {{Party name with colour|Scottish Liberal Democrats}}
| 4|| 3|| +1||+29
|-
| {{Party name with colour|Scottish National Party}}
| 19|| 29|| −10||–
|-
| {{Party name with colour|Scottish Greens}}
| 1|| 1|| –||+1
|-
| {{Party name with colour|Independent politician}}
| 22|| 9|| +13||+8
|-
|style="width: 5px; data-sort-value="Other"|
|style="text-align: left;" scope="row"| Other
| –|| 2|| −2||+3
|}

Thus, of 1223 seats filled in 2012, only 68 were filled by candidates who were not in top three or four spots in the first count. Therefore, transfers changed the outcome of only about 6 percent of the spots. [[Single non-transferable vote]] would have provided the same results in a great majority of cases.