This paper exposes the main issues involved in the development of a new and authentic Spain Consumer Price Index for the period of 1830 to 1936. The different sections in which it is arranged are focused on defining the field of study and scope to be analyzed, the sources and methodology used, as well as the similarities and differences in respect of other currently available indexes. It also contains a first and brief analysis of the results. The most outstanding characteristic of the new CPI from a long term perspective is its high stability, only once broken in a significant way during the 1914–1920 years, under the influence of World War I. The yearly growth rate for the whole of this period did not even reach 1 per cent, even though there was a change of level observed during the noted brief inflationary spike.
