The three measures have generally evolved broadly in line over time, although there have been instances when their behaviour has differed. For example, in the fourth quarter of 2016 their range was relatively wide—between 1.4 and 2.1 per cent (Chart 4).
To explore this behaviour, we based our analytical framework on the Phillips curve.19 We assume that core inflation depends on the degree of excess capacity in the economy and degree of ERPT.20 In the short run, inflation is also affected by relative price changes and other temporary demand and supply shocks.21 Chart 4: The new measures of core inflation have diverged recently Year-over-year percentage change, monthly data  % 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0  1995  1997  1999  2001  CPI-trim Source: Statistics Canada  19  2003  2005  2007  CPI-median  2009  2011  2013  2015  CPI-common Last observation: December 2016  There are various ways to represent and estimate the Phillips curve.