where MAD $=$ median absolute deviation and $N$ is the number of stars in each bin. It is encouraging that the Sgr stars in our RRL sample agree very well with the model predictions by [@law10]. Proper motion measurements of Sgr stars in the literature are also shown in Fig. \[fig:sgr\_pms\]: these are given by the orange diamonds [@koposov13], cyan squares [@sohn15; @sohn16] and grey triangles [@carlin12]. Our SDSS-*Gaia* proper motions are in excellent agreement with these other (independent) measures (see also Fig. \[fig:pm\_comp\]). Finally, we show the proper motions for the entire sample of SDSS-*Gaia* RRL stars with the open green circles. The stars associated with Sgr are clearly distinct from the overall halo in proper motion space. The solid black line shows the maximum likelihood model for halo rotation computed in Section \[sec:like\]. A model with mild prograde rotation agrees very well with the proper motion data. Note that the variation in proper motion with $\Lambda_\odot$ in the model is largely due to the solar reflex motion. Indeed, the solar reflex motion (in proper motion space) for Sgr stars is lower because they are typically further away than the halo stars. This is the main reason for the 