I've actually had the (dis)pleasure of doing a fair bit of work in this area and have found LinkedIn to be pretty directionally accurate - for tech companies, I

I've actually had the (dis)pleasure of doing a fair bit of work in this area and have found LinkedIn to be pretty directionally accurate - for tech companies, I'd ballpark it at closer to 80-90% in most cases. They may very well be one of the outliers - I typically saw that in businesses structured in a way that made it readily understandable (ie 75 core employees, but hundreds of hourly warehouse employees without LinkedIn accounts). Not sure if Theranos has such a structure - perhaps the medical/research side is much less likely to have LinkedIn accounts than the tech side.