However, for a variety of reasons, such trend analyses need to be viewed in the context of certain limitations. While the basic methodology and structure of the CFOI data have remained constant, several primary coding systems used to classify the data have changed substantially over the past two decades. For some code systems, we adjusted the case definition for our study to reduce the impact of differences (e.g., including selected vehicles, such as tractors, with machines). For other code schemes (e.g., industry), we constrained analyses to those years containing data that were coded based on a single coding system. While information on detailed subindustries and OIICS event and exposure is available from the CFOI data, analyses by these details were constrained by the number of fatalities relative to the number of categories for a given variable. The decision to focus on trends over time further constrained depth of analyses. Targeting prevention measures would benefit from identifying those industry, machine, and event combinations with the highest annual fatality rates. However, in most instances the number of annual cases in the industry, machine, and event combinations do not support such detailed analyses.