Mean estimates for Ṁ versus period of pulsation for the AGB stars in the sample are plotted in black. Different pulsational types are indicated with different plotting symbols: + for Miras,  ∗  for OH/IR stars, ∇ for SRa and  ⋄  for SRb type stars. The red  ∗  OH/IR data points were obtained from He & Chen (2001,priv. comm.). A linear relation fits the Miras, OH/IR stars and semi-regular variables in our sample with periods shorter than 850 days. Ṁ levels off to a constant value of 2.6 × 10^-5 M_⊙  yr^-1 for longer periods. The darker shaded region represents a factor three spread around this fit, the paler grey region represents a spread of a factor 10. See Sect. 5.1.3 for further details.