Here's the all-time outdoor list (Dibaba ran 8:15 indoors) going down to Simpson's pr with known dopers, Chinese, and Eastern Europeans removed (Szabo otherwise would appear all over this list; she did not only carry drugs in her car but also ran a ton of times in the 8:20s), except for Slaney, who holds the American record and in any case didn't test positive until a decade or so later. You can see that almost all the times were run in July, August, or September. There are a few at the very end of June, but there are also quite a few from this very meet. 2014 in particular was notable where Ayana and Dibaba finished 5th and 6th, yet ran 8:24 and 8:26, respectively. Of course, I believe many on this list cheated, especially Dibaba, given the Sabadell incident, but at any rate, you can see that this race very much has the possibility of providing Simpson pacing sufficient to break Slaney's record but it will be very tough. Her best is four seconds slower and that was later in the season. On the positive side, she has the drafting, the pacing, the competition, and has shown the strength even to run a fast time while leading the whole field. She is almost as fast as Slaney at 1500m and she beat Rowbury, who has since set the 5000m and 1500m AR's. It is a good thing that she is sharpening beforehand by going after the 2M record.
7 8:20.68 Helen Obiri KEN 13.12.89 1 Ad-Dawhah 09.05.2014
8 8:21.14 Mercy Cherono KEN 07.05.91 2 Ad-Dawhah 09.05.2014
11 8:21.64 Sonia O'Sullivan IRL 28.11.69 1 London 15.07.1994
14 8:22.20 Paula Radcliffe GBR 17.12.73 2 Monaco 19.07.2002
15 8:22.22 Almaz Ayana ETH 21.11.91 1 Rabat 14.06.2015
16 8:22.34 Almaz Ayana ETH 21.11.91 1 Zürich 03.09.2015
19 8:23.11 Almaz Ayana ETH 21.11.91 1 Ad-Dawhah 06.05.2016
20 8:23.14 Helen Obiri KEN 13.12.89 1 Monaco 21.07.2017
21 8:23.23 Edith Masai KEN 04.04.67 3 Monaco 19.07.2002
23 8:23.55 Faith Kipyegon KEN 10.01.94 3 Ad-Dawhah 09.05.2014
27 8:24.27 Helen Obiri KEN 13.12.89 1 Monaco 15.07.2016
29 8:24.41 Viola Kibiwott KEN 22.12.83 4 Ad-Dawhah 09.05.2014
30 8:24.51+ Meseret Defar ETH 19.11.83 1 Bruxelles 14.09.2007
31 8:24.58 Almaz Ayana ETH 21.11.91 5 Ad-Dawhah 09.05.2014
32 8:24.66 Meseret Defar ETH 19.11.83 1 Stockholm 25.07.2006
37 8:25.62 Berhane Adere ETH 21.07.73 3 Zürich 17.08.2001
39 8:25.83 Mary Slaney USA 04.08.58 1 Roma 07.09.1985
40 8:25.92 Gelete Burka ETH 15.02.86 2 Stockholm 25.07.2006
41 8:26.14 Berhane Adere ETH 21.07.73 1 Bruxelles 30.08.2002
43 8:26.21 Genzebe Dibaba ETH 08.02.91 6 Ad-Dawhah 09.05.2014
45 8:26.36 Mercy Cherono KEN 07.05.91 2 Ad-Dawhah 06.05.2016
47 8:26.48 Zahra Ouaziz MAR 20.12.69 2 Zürich 11.08.1999
49 8:26.54 Genzebe Dibaba ETH 08.02.91 2 Zürich 03.09.2015
53 8:26.97 Paula Radcliffe GBR 17.12.73 5 Roma 29.06.2001
54 8:27.01 Zahra Ouaziz MAR 20.12.69 2 Bruxelles 03.09.1999
58 8:27.17 Edith Masai KEN 04.04.67 3 Stockholm 25.07.2006
62 8:27.24 Meseret Defar ETH 19.11.83 1 Stuttgart 23.09.2007
63 8:27.25 Mercy Cherono KEN 07.05.91 2 Monaco 15.07.2016
64 8:27.26 Zahra Ouaziz MAR 20.12.69 2 Paris 29.07.1998
65 8:27.40 Paula Radcliffe GBR 17.12.73 3 Zürich 11.08.1999
66 8:27.57 Sonia O'Sullivan IRL 28.11.69 1 Zürich 16.08.1995
67 8:27.58 Sonia O'Sullivan IRL 28.11.69 2 Zürich 11.08.2000
68 8:27.62 Getenesh Wami ETH 11.12.74 4 Zürich 17.08.2001
73 8:28.07 Paula Radcliffe GBR 17.12.73 5 Zürich 17.08.2001
74 8:28.26 Zahra Ouaziz MAR 20.12.69 2 Oslo 30.06.1999
75 8:28.33 Janet Kisa KEN 05.03.92 3 Monaco 15.07.2016
77 8:28.41 Sentayehu Ejigu ETH 21.06.85 1 Monaco 22.07.2010
78 8:28.49 Gelete Burka ETH 15.02.86 3 Ad-Dawhah 06.05.2016
79 8:28.51 Irene Jelagat KEN 10.12.88 7 Ad-Dawhah 09.05.2014
80 8:28.66 Zahra Ouaziz MAR 20.12.69 1 Nice 16.07.1998
80 8:28.66 Vivian Cheruiyot KEN 11.09.83 2 Stuttgart 23.09.2007
80 8:28.66 Beatrice Chepkoech KEN 06.07.91 2 Monaco 21.07.2017
84 8:28.72 Zahra Ouaziz MAR 20.12.69 2 Roma 07.07.1999
85 8:28.74 Sonia O'Sullivan IRL 28.11.69 1 Oslo 10.07.1993
87 8:28.82 Sonia O'Sullivan IRL 28.11.69 2 Nice 16.07.1998
88 8:28.83 Zola Pieterse GBR 26.05.66 3 Roma 07.09.1985
89 8:28.85 Paula Radcliffe GBR 17.12.73 4 Zürich 11.08.2000
90 8:28.87 Maryam Yusuf Jamal BRN 16.09.84 1 Oslo 29.07.2005
91 8:28.90 Sifan Hassan NED 01.01.93 1 Birmingham 20.08.2017
92 8:28.95 Mercy Cherono KEN 07.05.91 1 Bruxelles 05.09.2014
93 8:29.02 Yvonne Murray GBR 04.10.64 3 Seoul 25.09.1988
94 8:29.06 Priscah Cherono KEN 27.06.80 3 Stuttgart 23.09.2007
95 8:29.14 Lydia Cheromei KEN 11.05.77 5 Zürich 11.08.2000
96 8:29.20 Maryam Yusuf Jamal BRN 16.09.84 2 Monaco 22.07.2010
97 8:29.24 Getenesh Wami ETH 11.12.74 3 Paris 29.07.1998
101 8:29.38 Sifan Hassan NED 01.01.93 2 Bruxelles 05.09.2014
102 8:29.41 Genzebe Dibaba ETH 08.02.91 3 Bruxelles 05.09.2014
103 8:29.45 Maryam Yusuf Jamal BRN 16.09.84 1 Zürich 19.08.2005
105 8:29.55 Tirunesh Dibaba ETH 01.06.85 1 London 28.07.2006
106 8:29.58 Jennifer Simpson USA 23.08.86 4 Bruxelles 05.09.2014
