OBJECTIVES: Health technology appraisal bodies such as NICE in the UK have shown interest in using the absolute and proportional quality adjusted life year (QALY) shortfall to represent aspects of disease burden. NICE originally proposed in their value based assessment consultation paper that additive cost-effectiveness threshold weightings could be applied according to both the absolute and proportional QALY shortfalls. This analysis sought to understand the relationship between the absolute and proportional shortfall and therefore whether the proposal by NICE was justified. METHODS: The conditions selected were identified from NICE single technology appraisals published between July 2011 and December 2014. The age that treatment commenced was taken from manufacturer models and combined with the gender-dependent average life expectancy and age- and gender-dependent utilities in the UK to calculate the discounted QALYs accrued by a healthy person (X). Discounted QALYs accrued by current treatment were extracted from manufacturer submissions (Y). Consequently, absolute (X-Y) and proportional (absolute/X) QALY shortfalls were calculated for each condition. The data were analysed using linear OLS regression, with the absolute shortfall being the dependent variable. Appraisals were excluded if the manufacturer submission was missing or if the time horizon was not lifetime. RESULTS: The absolute and proportional QALY shortfalls were calculated for 43 conditions. The regression line had equation y = 13.0x + 0.005 and the r-squared value was 0.84, indicating that there is a strong positive correlation between absolute and proportional QALY shortfall. This is not surprising given that the variables are mathematically coupled. CONCLUSIONS: Absolute and proportional QALY shortfall are not independent variables, but are mathematically related, and therefore bodies such as NICE should avoid assigning additive weights to these measures. If additive weights were assigned, conditions where the QALY does not fully capture the benefits of new technologies would be particularly disadvantaged.