This is Part I of a two-part article that reviews methodological and statistical challenges involved in the estimation of humanity’s technological capacity to communicate, store, and compute information. It is written from the perspective of the results of our recent inventory of 60 technological categories between 1986 and 2007 (measured in bits and MIPS [million-instructions-per-second]). In Part I, we summarize the results of our inventory, and explore a series of basic choices that must be made in the course of measuring information and communication capacities. The most basic underlying assumptions behind our estimates include—among others—decisions about what is counted as (1) communication, (2) storage, and (3) computation; if technological capacities or consumption of information is measured; and if unique information is distinguished from duplicate information. We compare our methodological choices with different approaches taken in similar studies. The article shows how the particular question on the researcher’s mind, as well as the availability of source data has and will influence most of the methodological choices in different exercises.