No credible source says 1.7, the source that says this must be based on some kinda UN projection of 2010. Real TFR is probably around 1.0, in some parts of china it's below 0.7 (in the northeast it's around this number, in Macao it's 0.4). A lot of other countries are completely fucked as well and google pushes up UN projections from years ago (Like colombia UN projects the fertility rate to be higher in 2100 than it is according to the official numbers right now).
