How many labs like this one are there in the world ? Are there 20,000 of them ? Are there 7 ?
Of the labs like this one in the world, how many of them are doing GoF research on coronaviruses ? 1200 of them ? 1 of them ?
This won't be conclusive but given the reasonable heuristics that I work with, having a sense of these proportions would go a long way ...
Of course far more virology labs exist in the world. But since this pandemic is SARS-like, the correct comparison is only labs working with SARS-like viruses, weighted by amount of such work.
Also worth noting that gain of function may be a distraction. It's entirely possible that SARS-CoV-2 is a naturally-evolved virus but still emerged due to WIV staff activity, either from culture in their lab or just from a researcher who got infected while sampling. The WIV's sampling program was the biggest in the world, visiting remote caves known to be inhabited by infected bats, to bring back samples to be cultured, sequenced, and otherwise manipulated.
If the virus was manipulated in the lab (by genetic engineering, serial passaging, etc.), then it was probably starting from a novel natural virus. Many virologists seeking to exclude a lab origin have noted correctly that SARS-CoV-2 shows no signs of being derived in any known way from any known virus; so the WIV's (considerable) ability to sample new viruses from nature seems more significant to me than their ability to engineer them in the lab.
And just to address the frequent and wrong counterarguments:
1. The WIV is not located in an expected natural spillover zone. Their sampling trips were to Yunnan and surroundings, near Kunming or Pu'er, about 900 miles away.
2. If this was a naturally-evolved virus, then the probability that it was spread by an infected WIV researcher isn't [# of WIV researchers]/[# of total people in Wuhan]. WIV researchers are a vanishingly small fraction of the total population of Wuhan, but they're a large fraction of the total population traveling from remote bat caves in Yunnan back to Wuhan. An expert deliberately seeking novel viruses is far more likely to find one than a merely reckless wildlife smuggler. In theory the expert knows the risks better and will take precautions; but many photographs exist of WIV researchers handling animals with nothing more than a surgical mask and nitrile gloves.
3. The WIV certainly hadn't published every virus they'd collected. For example, RaTG13, the closest known animal virus to SARS-CoV-2, was reportedly collected by them in 2013, but published only after the pandemic emerged. Marc Lipsitch notes that if a researcher had become infected on a sampling trip, then the WIV might never even have sequenced the virus before the pandemic emerged.
To be clear, nothing above says SARS-CoV-2 definitely emerged due to WIV staff activity. The arguments that it definitely didn't all boil down to "because the WIV says it didn't", though, and China has thoroughly obstructed any attempt to audit that claim. It's possible that they're obstructing for a different reason--for example, the CCP's favored "frozen food" theory seems to be trying to exclude not only WIV lab origin, but origin anywhere in China, natural or otherwise. Nevertheless, I'm shocked to see how many people are willing to take the same one-man dictatorship that claims the camps in Xinjiang are for voluntary job training at its word.