The ONS are produce new methods to estimate population changes from administrative data.
You can see there estimates for 2011 and 2015 populations with this app:-
The official population estimates produce an unbelieving rise in population in Coventry over the 4 years
| Census/official | Nuneaton | Coventry | Warwick | Rugby | North Warks | Stratford | Total |
| 2011 Census | 125,252 | 316,960 | 137,648 | 100,075 | 62,014 | 120,485 | 862,434 |
| 2015 Mid Year estimate | 126,319 | 345,385 | 139,931 | 103,443 | 62,787 | 121,522 | 899,387 |
| Growth | 1,067 | 28,425 | 2,283 | 3,368 | 773 | 1,037 | 36,953 |
The new SPD method produces only a slightly lower increase but it is spread more evenly over the region. It is also interesting that the estimated total population for Coventry and Warwickshire is 10,000 higher than the official estimate in 2011 and 9,000 higher in 2015. This is not necessary an error as the new method will pick up more people missed by the census and people who have more than one home.
| SPD V2.0 total population | Nuneaton | Coventry | Warwick | Rugby | North Warks | Stratford | Total |
| 2011 | 126,755 | 326,279 | 135,473 | 99,141 | 62,290 | 122,471 | 872,409 |
| 2015 | 130,313 | 344,612 | 139,749 | 105,126 | 63,407 | 125,358 | 908,565 |
| Growth | 3,558 | 18,333 | 4,276 | 5,985 | 1,117 | 2,887 | 36,156 |
If the new method is accurate then we need considerably less housing for Coventry overspill.
The ONS has released a research report on internal migration which has been tested on the migration between 2015 and 2016.
It shows more possible significant errors in 2016 population errors
For Coventry net internal migration out is 0.6% of the population compared to official estimate of 0.12%. That could take the estimated population for Coventry down by 1,600 for just one years change.