Transfer functions are the only pointing facilitation technique actually used in modern graphical interfaces involving the in- direct control of an on-screen cursor. But despite their gen- eral use, very little is known about them. We present Echo- Mouse, a device we created to characterize the transfer func- tions of any system, and libpointing, a toolkit that we devel- oped to replicate and compare the ones used by Windows, OS X and Xorg. We describe these functions and report on an experiment that compared the default one of the three sys- tems. Our results show that these default functions improve performance up to 24% compared to a unitless constant CD gain. We also found significant differences between them, with the one from OS X improving performance for small target widths but reducing its performance up to 9% for larger ones compared to Windows and Xorg. These results notably suggest replacing the constant CD gain function commonly used by HCI researchers by the default function of the con- sidered systems.