All births in England linked to delivery HES records by year of birth, 2005–2014.
| Year of birth | Number of ONS birth records | Linked to HES delivery record | Never linked to HES delivery record | Linkage rate |
| 2005 | 617 613 | 582 963 | 34 650 | 94.39 |
| 2006 | 640 271 | 607 649 | 32 622 | 94.90 |
| 2007 | 659 061 | 632 039 | 27 022 | 95.90 |
| 2008 | 676 999 | 655 511 | 21 488 | 96.83 |
| 2009 | 675 330 | 657 622 | 17 708 | 97.38 |
| 2010 | 687 100 | 673 566 | 13 534 | 98.03 |
| 2011 | 688 681 | 674 751 | 13 930 | 97.98 |
| 2012 | 698 457 | 681 677 | 16 780 | 97.60 |
| 2013 | 668 433 | 651 957 | 16 476 | 97.54 |
| 2014 | 664 967 | 647 047 | 17 920 | 97.31 |
| Total | 6676 912 | 6464 782 | 212 130 | 96.82 |
39689.65073 Pearson χ 2 statistic.
9 <- df = (rows−1)×(columns− 1).
0.0000 <- getting the P value from the χ2 statistics and the df.
HES, Hospital Episode Statistics; ONS, Office for National Statistics.