text: We follow the method of Kelly et al. [9], who model 
  quasar optical light curves as a continuous time ﬁrst- 
  order autoregressive process (CAR(1)) in order to ex- 
  tract characteristic time scales and the amplitude of 
  ﬂux variations. Although ﬂaring behavior is not typi- 
  cally thought of as an autoregressive process, we ﬁnd 
  that the light curves are well-ﬁt by the models and 
  therefore adopt the method here to study blazar sub- 
  millimeter light curves. 
  
  Figure 3: Characteristic timescale (days) versus 
  submillimeter luminosity (erg s−1) in the 1mm band for 
  all objects. Physically, τ represents a “relaxation 
  timescale”, the timescale beyond which events are no 
  longer correlated. 
  
  The CAR(1) process is described by a stochastic 
  diﬀerential equation [9], 
  
  √ 
  
  1 
  τ 
  dS(t) =  S(t) dt + σ  dt (cid:15) (t) + b dt,  (3) 
  
  both classes extending across a large range in τ . Be- 
  cause of the uncertainty for objects with shorter char- 
  acteristic timescales, it is hard to draw any deﬁnitive 
  conclusions about the diﬀerences between classes. It 
  is important to note that τ does not necessarily rep- 
  resent a ﬂaring timescale, which is a behavior that 
  typically operates on a scale of ∼10–100 days and not 
  on the longer timescales we see in τ . 
  
  (4) 