This is my more detailed analysis of the western councils of Derry Strabane, Fermanagh Omagh and Mid Ulster. The party change in council vote between 2011 and 2014 was:

 

  Derry Strabane 2014 Derry Strabane 2011 Change
       
SF 19384 20845 -1461
SDLP 13792 17410 -3618
Nationalist 5909 5832 77
Alliance 853 359 494
Green 0 0 0
NI21 0 0 0
UUP 4065 4001 64
DUP 8273 10120 -1847
TUV 521 0 521
PUP 274 204 70
UKIP 694 0 694
Unionist 0 0 0
Conservative 0 0 0
       
Total 53765 58771 -5006

 

There was a large decline in the SDLP vote (mainly in Derry) and a lesser decline in the SF vote. The DUP vote was also down, more so than the SF vote. Overall, there was a 5,000 vote decline in the nationalist vote, a 500 vote decline in the unionist vote and a 494 vote increase in Alliance vote. The increased Alliance vote is due to competing in more DEA’s. Some unionist voters in the Euro election (TUV, PUP and UKIP) did not vote in the council election due to their party not standing in some DEA’s and some unionist votes and nationalist votes were lost to Alliance. The unionist vote may have been down minimally when taking into account these factors. The biggest surprise here was the collapse of the SDLP vote. Since the SF vote also declined and the independent nationalist vote barely increased the SDLP and SF voters stayed home. Dissident republicans and other independent nationalists benefited with an IRSP seat in Sperrin and 3 independents in Derry.

In Fermanagh Omagh the change in party vote between 2011 and 2014 was:

 

  Fermanagh Omagh 2014 Fermanagh Omagh 2011 Change
       
SF 19486 21629 -2143
SDLP 7164 6810 354
Nationalist 2214 4145 -1931
Alliance 819 443 376
Green 71 63 8
NI21 0 0 0
UUP 9612 10558 -946
DUP 7075 8956 -1881
TUV 1091 309 782
PUP 0 0 0
UKIP 296 0 296
Unionist 0 0 0
Conservative 0 0 0
       
Total 47828 52913 -5085

 

There was a 3720 vote decline in the nationalist vote and a 1749 decline in the unionist vote. The SDLP vote increased and there was a large decline in the SF and independent nationalist vote. The improved SDLP vote led to additional councilors in Erne East and Omagh Town. The decline in nationalist and unionist turnout was proportional to their share of the electorate though the true unionist decline would have been less since some Euro unionist voters did not vote in the council election.

In Mid Ulster the change in party vote between 2011 and 2014 was:

  Mid Ulster 2014 Mid Ulster 2011 Change
       
SF 22287 24167 -1880
SDLP 7600 9381 -1781
Nationalist 2571 2889 -318
Alliance 450 298 152
Green 0 0 0
NI21 0 0 0
UUP 9574 9145 429
DUP 9723 11361 -1638
TUV 2370 2638 -268
PUP 0 0 0
UKIP 195 0 195
Unionist 118 0 118
Conservative 0 0 0
       
Total 54888 59879 -4991

 

The nationalist vote declined 3,979 and the unionist vote declined 1164. The true unionist decline would have been less. The main surprises were the loss of a SF seat to the SDLP in Dungannon and the loss of an expected SDLP seat in Moyola to the UUP that was due to the decline in nationalist turnout.

I have calculated the unionist and nationalist turnout in all DEA’s using the 2011 voting age population as recorded in the 2011 census. For example, Erne North had a Catholic electorate of 5,577, a Protestant electorate of 5,290 and Other/None of 257 and I estimated the overall nationalist electorate at ~5,700 and the unionist electorate ~5,400. The SF-SDLP vote was 2,589 for a turnout of 45%. The unionist party vote was 3,701 for a turnout of 69%. The Protestant electorate has not changed since 2011 so the unionist turnout figures should be very accurate though they underestimate unionist turnout in some DEA’s where the TUV or UKIP did not compete since some of those voters voted in the Euro election but not the council election. The nationalist turnout figures probably overestimate the nationalist turnout by 1% to 3% because they do not account for the increase in the nationalist electorate since 2011, which would be over 20,000 for all of Northern Ireland.

Turnout DEA Nationalist Unionist
     
Erne East 6 67% 70%
Erne West 5 66% 66%
Erne North 5 45% 69%
Enniskillen 6 42% 49%
Omagh 6 37% 50%
Mid Tyrone 6 67% 67%
West Tyrone 6 56% 68%
Clogher Valley 6 55% 71%
Dungannon 6 39% 57%
Torrent 6 48% 63%
Cookstown 7 49% 59%
Magherafelt 5 48% 54%
Moyola 5 59% 60%
Carntogher 5 63% 54%
Derg 5 62% 65%
Sperrin 7 52% 54%
Faughan 5 41% 43%
Waterside 7 43% 48%
Foyleside 5 47% NA
Ballyarnett 6 49% NA
The Moor 5 57% NA

 

Carntogher DEA is the only DEA in which nationalist turnout was higher than unionist turnout. There are 7 DEA’s where nationalist turnout is similar to unionist turnout. In half the DEA’s nationalist turnout is much lower than unionist turnout. Indeed, even though the Catholic electorate in the Erne North, Enniskillen and Clogher Valley DEA’s exceeds the Protestant electorate, the unionist vote was higher than the nationalist vote in all 3 of those DEA’s!

What would have been the outcome for Westminster and Assembly elections if they had been held the same day? Here are the estimated vote totals and percentages.

Westminster Assembly Foyle West Tyrone FST Mid Ulster
         
SF 12035 16886 14074 18267
SDLP 11391 6111 5488 5772
Nationalist 4244 1818 3521 1231
Alliance 853 671 401 117
Green 0 198 71 0
NI21 0 0 0 0
UUP 2056 5239 10560 5932
DUP 4512 6993 7763 5761
TUV 0 521 1587 1884
PUP 274 0 0 0
UKIP 696 0 296 195
Unionist 0 0 0 0
Conservative 0 0 0 0
         
Total 36061 38437 43761 39159
         
SF 33.37% 43.93% 32.16% 46.65%
SDLP 31.59% 15.90% 12.54% 14.74%
Nationalist 11.77% 4.73% 8.05% 3.14%
Alliance 2.37% 1.75% 0.92% 0.30%
Green 0.00% 0.52% 0.16% 0.00%
NI21 0.00% 0.00% 0.00% 0.00%
UUP 5.70% 13.63% 24.13% 15.15%
DUP 12.51% 18.19% 17.74% 14.71%
TUV 0.00% 1.36% 3.63% 4.81%
PUP 0.76% 0.00% 0.00% 0.00%
UKIP 1.93% 0.00% 0.68% 0.50%
Unionist 0.00% 0.00% 0.00% 0.00%
Conservative 0.00% 0.00% 0.00% 0.00%

 

For Stormont there would be no change in Mid Ulster and West Tyrone. It would be 3 SF, 1 SDLP, 1 UUP and 1 DUP in both constituencies. For Westminster, there would also be no change in Mid Ulster and West Tyrone.  In Foyle, there would be no change with 3 SDLP, 2 SF and 1 DUP.  Although the SF  vote exceeds the SDLP in the 2011 election 80% of the unionist surplus transferred to the SDLP as well as much of the Alliance vote. As there was 7% unionist surplus 5.5% of that, along with 1.5% of the Alliance vote would bring the SDLP total up to 38.5%, far exceeding the SF percentage. Westminster could be a different outcome. The SF vote is ~650 higher than the SDLP vote. However, in the 2010 election, approximately 20% of the unionist vote voted tactically for the SDLP, which would have been 1,500 votes in this election. The big unknown would be how the 4,244 independent nationalist would vote. Of course, many of the dissident republican voters may not vote in a Westminster election so it is difficult to predict the outcome in 2015.

In Fermanagh South Tyrone the UUP vote exceeded the DUP vote by over 6% so it appears that the UUP would pick up an Assembly seat from the DUP. The SDLP would also pick up a seat from SF. At 12.54% they would pick up enough of the unionist surplus and Alliance transfers to reach a quota and would receive some of the 8% independent nationalist transfers. It appears that SF would lose a Westminster seat to a unionist unity candidate. There are several reasons for this. The Dungannon DEA does not match the Westminster boundaries. A section of Killyman ward with 400 to 500 unionists is actually in the Craigavon council and another section with 400 to 500 nationalist votes is actually in Mid Ulster. So the unionist vote would be 1% higher and the nationalist vote 1% lower based on the actual Westminster boundaries. Another reason is that EU nationals are not permitted to vote in Westminster elections. There were 3,000 EU nationals on the electoral register for the council elections and if 800 of these voted there would be another 1% shift in the nationalist unionist balance. The last reason is that the actual unionist vote total is higher because some TUV and UKIP voters that voted in the Euro election did not vote in the council election due to the lack of candidates. There were no such candidates in Clogher Valley and Erne West. I estimate and additional 400+ unionist votes. So with the Westminster electorate the combined nationalist vote would be at most 51% and the unionist vote would be at least 48%. The SDLP vote was 7.6% in 2010 and would need to collapse to less than 3% for SF to win. This is unlikely to occur. Unless there is an end to nationalist apathy a unionist unity candidate will win Westminster in 2015.