A while ago I calculated the average improvement for Nike vs. non-Nike athletes who had a SB in both 2016 and 2019 listed on the alltime-athletics site (about 50 such athletes). The assumption was the Nike athletes wore Vaporflys in 2019 and not 2016 (Kipchoge and Bekele excluded). On average the non-Nike athletes ran 76 seconds slower in 2019 than 2016 while Nike athletes ran 55 seconds faster, for a net difference of 131 seconds.
Non-Nike
Athlete SB_2019 SB_2016 Improvement
Albert Korir 2:08:03 2:10:08 125
Yohanes Gebregerish 2:08:26 2:09:48 82
Evans Chebet 2:05:00 2:05:31 31
Sammy Kigen 2:08:12 2:08:19 7
Yuki Kawauchi 2:09:21 2:09:11 -10
Robert Chemosin 2:10:09 2:09:48 -21
Raymond Choge 2:09:02 2:08:39 -23
Lemi Berhanu 2:05:09 2:04:33 -36
Tadesse Abraham 2:07:24 2:06:40 -44
Lucas Rotich 2:09:48 2:08:53 -55
Felix Kandie 2:08:07 2:06:25 -102
Martin Kosgei 2:10:19 2:07:22 -177
Festus Talam 2:09:25 2:06:26 -179
Daniel Wanjiru 2:08:40 2:05:21 -199
Sammy Kirop Kitwara 2:09:52 2:05:45 -247
Wilson Kipsang Kiprotich 2:09:18 2:03:13 -365
Non-Nike average improvement -75.8
Nike
Athlete SB_2019 SB_2016 Improvement
Dejene Debela 2:05:46 2:10:13 267
Asefa Mengistu 2:04:24 2:08:41 257
Evans Korir 2:07:09 2:10:04 175
Kelkile Gezahegn 2:06:09 2:08:56 167
Laban Mutai 2:06:40 2:09:16 156
Thomas Kiplagat 2:06:00 2:08:34 154
Mule Wasihun 2:03:16 2:05:44 148
Philemon Rono 2:05:00 2:07:20 140
Stephen Mokoka 2:07:58 2:10:18 140
Reuben Kerio 2:07:00 2:09:06 126
Marius Kipserem 2:04:11 2:06:11 120
Sisay Lemma 2:03:36 2:05:16 100
Lawrence Cherono 2:05:45 2:07:24 99
Barnabas Kiptum 2:08:02 2:09:21 79
Limenih Getachew 2:07:30 2:08:48 78
Solomon Deksisa 2:05:16 2:06:22 66
Chala Dechase 2:08:25 2:09:19 54
Kaan Kigen Özbilen 2:05:27 2:06:10 43
Edwin Koech 2:08:24 2:09:06 42
Yihunilign Adane 2:09:11 2:09:48 37
Dominic Ruto 2:09:43 2:09:28 -15
Abera Kuma 2:08:14 2:07:48 -26
Stephen Kiprotich 2:08:31 2:07:46 -45
Dickson Chumba 2:08:44 2:07:34 -70
Yitayal Atnafu Zerihun 2:10:08 2:08:53 -75
Gilbert Koech 2:09:57 2:08:04 -113
Cyprian Kotut 2:09:18 2:07:11 -127
Geoffrey Kirui 2:08:54 2:06:27 -147
Laban Korir 2:09:36 2:05:54 -222
Nike average improvement 55.4
Excluded because they wore VFs both years
Kenenisa Bekele 2:01:41 2:03:03 82
Eliud Kipchoge 2:02:37 2:03:05 28
Excluded because I didn't know sponsor
Emmanuel Kichwen 2:08:42 2:10:15 93
Birhanu Teshome 2:08:20 2:09:05 45