From a 2017 paper, https://arxiv.org/abs/1703.02874v1
> First, we show that devices commonly make improper use of randomization by sending wireless frames with the true, global address when they should be using a randomized address. We move on to extend the passive identification techniques of Vanhoef et al. to effectively defeat randomization in ~96% of Android phones. Finally, we show a method that can be used to track 100% of devices using randomization, regardless of manufacturer, by exploiting a previously unknown flaw in the way existing wireless chipsets handle low-level control frames.
and near the end of section 4.2
> Therefore we posit that much less than ∼50% of devices conduct randomization.