Which non-resident capital flows are the biggest driver of EM FX? If you look across all EMs, other investment flows (red), which are mostly bank lending, are the most correlated with EM FX (orange), followed closely by portfolio flows (blue) and then, least of all, FDI. 
But looking at a broad EM aggregate is quite misleading, because China has such an outsize influence. Looking at China only, other investment is by far the biggest driver of the RMB versus the Dollar, while portfolio and FDI flows are much less important.
For the rest of EM (excluding China) the pattern is completely different. While for China it is bank-based (other investment) flows that are the key driver of FX, for the rest of EM it is portfolio flows (blue) that are dominant. Portfolio flows might be the marginal flow in EM.
