I can only speak for the U.S. but there are three sources that can be utilized and are utilized by the Fed. The first is a measure of market based expectations where inflation-linked bonds are available and can be measured as the spread between a nominal rate and the corresponding real rate. The second can be based on consumer surveys and the University of Michigan has a medium term measure of expectations. The third is based on the forecasts of economic forecasters, which is put together in the US by the Philadelphia Fed. Some of these measures are presented and discussed in the Fed' monetary policy report released today http://www.federalreserve.gov/monetarypolicy/files/20140211_mprfullreport.pdf

These are also the three approaches available in Australia.

Collective bargaining settlement data is useful especially for multi-term agreements. For example, many recent Canadian /US agreements are for longer terms and with smaller increases evidence of lower inflation expectations going forward.