Many leases escalate the lease rates each year based on the change in the Consumer Price Index. In Oregon and southern Washington, the Portland-Salem index is likely the index cited.
The link to the web page with this information is http://www.bls.gov/ro9/ro9_or.htm. Go down to the News Releases section and select the “Portland-Salem, OR-WA (Semiannual News Release)” HTML or PDF link.
The semi-annual CPI Index comes out in July or August (for Jan thru June) and the Annual CPI for the each prior year comes out in February or March.
The full list of Western News Releases and Indexes can be found at http://www.bls.gov/ro9/news.htm.