Fig. 4.

Comparison of methods used in the base-case analysis (x axis) and those used as alternatives in a robustness analysis (y axis) for the articles between 2003–2009 and 2009–2015 for missing costs and effects. Legend: unspecified methods (Unclear), other methods (Others), linear extrapolation (Lin Ext), last value carried forward (LVCF), mean imputation (Mean), conditional imputation (Cond), complete case analysis (CCA), multiple imputation (MI). The category “Unclear” includes those articles for which it was not possible, based on the text, to understand the methodology used to deal with the missingness, while the category “Others” consists of the following methods: random draw, linear mixed-effects model, expectation-maximisation algorithm, input-case analysis, assumed zeros, two-part regression