More recently, he (along with Prof. Susan Athey) has been working on using machine learning methods, particularly modifications to random forests called causal forests<ref>{{cite web |title=Causal Tree R package; Authors -- Susan Athey, Guido Imbens, Yangyang Kong & Vikas Ramachandra |url=https://github.com/susanathey/causalTree/blob/master/doc/briefintro.pdf}}</ref><ref>{{cite web |title=Recursive partitioning for heterogeneous causal effects; Authors -- Susan Athey and Guido Imbens |url=https://www.pnas.org/content/113/27/7353.short |access-date=13 October 2021 |archive-date=29 July 2021 |archive-url=https://web.archive.org/web/20210729101951/https://www.pnas.org/content/113/27/7353.short |url-status=live }}</ref> to estimate heterogeneous treatment effects in causal inference models. | More recently, he (along with Prof. Susan Athey) has been working on using machine learning methods, particularly modifications to random forests called causal forests<ref>{{cite web |title=Causal Tree R package; Authors -- Susan Athey, Guido Imbens, Yangyang Kong & Vikas Ramachandra |url=https://github.com/susanathey/causalTree/blob/master/doc/briefintro.pdf}}</ref><ref>{{cite web |title=Recursive partitioning for heterogeneous causal effects; Authors -- Susan Athey and Guido Imbens |url=https://www.pnas.org/content/113/27/7353.short |access-date=13 October 2021 |archive-date=29 July 2021 |archive-url=https://web.archive.org/web/20210729101951/https://www.pnas.org/content/113/27/7353.short |url-status=live }}</ref> to estimate heterogeneous treatment effects in causal inference models. |