A systematic review of the willingness-to-accept and willingness-to-pay disparities in empirical studies in the healthcare field

Willingness-to-pay (WTP) and willingness-to-accept (WTA) are widely used measures of individual preferences in valuing healthcare services; however, a persistent disparity between them, often with WTA exceeding WTP, raises concerns. This study aims to review empirical research evidence to achieve a comprehensive understanding of the disparity between WTA and WTP for health outcomes or healthcare goods and services. A search was conducted in PubMed, Embase, Web of Science, and Scopus from inception to November 15, 2023, for empirical research articles reporting both WTA and WTP in the healthcare field. Data extracted from the included studies encompassed WTA and WTP values, participation response rates, and other study characteristics. Descriptive analyses were conducted to compare WTA/WTP ratios across studies, and chi-square tests were applied to examine differences in response rates where applicable. A total of 779 records were identified through database searches. After removing duplicates, 405 records remained for title and abstract screening. Of these, 70 articles were retrieved for full-text review, and 28 articles met the eligibility criteria for inclusion in the final qualitative analysis, encompassing 35 distinct studies or subgroups. The reported WTA/WTP ratios ranged from 0.14 to 29.19, with a median value of 1.61, indicating that individuals often demand higher compensation to give up healthcare benefits than they are willing to pay to obtain them. Among the empirical studies analyzed, 29 studies (82.86%) from 24 articles reported WTA values that exceeded WTP values, while 6 studies (17.14%) from the remaining 4 articles indicated WTA values lower than WTP values. Among the 14 studies reporting both WTA and WTP response rates, six studies indicated a significantly lower WTA response rate compared to the WTP response rate, whereas two studies found the WTA response rate to be significantly higher (P < 0.05). The WTP response rate was observed to range from 0.89 to 20.23 times that of the WTA response rate. The results of this study suggest that losses in health outcomes or healthcare goods and services are valued differently than gains. The disparities between WTA and WTP are influenced by various factors, including the income effect and personal preferences. Individual preferences shape perceptions of WTA and WTP questions, resulting in varied response rates. Considering these disparities in the medical and healthcare fields can assist policymakers in making more informed decisions regarding the allocation of medical and health resources.