PurposePrior studies on the impact of incentives on physicians’ online participation mainly focused on different incentives while ignoring the difficulty of setting monetary incentives efficiently. Based on goal-setting theory, the current research examines the relationship between incentives with goals of varying difficulty and professional health knowledge sharing (PHKS) in online health knowledge-sharing platforms (OHKSPs).Design/methodology/approachFour field experiments with different monetary incentives were conducted by one of China’s largest OHKSPs, with whom the researchers cooperated in data collection. Monthly panel data on 10,584 physicians were collected from September 2018 to December 2019. There were 9,376 physicians in the treatment group and 1,208 in the control group. The authors used a difference-in-difference (DID) model to explore the research question based on the same control group and the Chow test with seemingly unrelated estimation (sureg) to compare regression coefficients between four groups. Several robustness checks were performed to validate the main results, including a relative time model, multiple falsification tests and a DID estimation using the propensity score matching method.FindingsThe results show that the monetary incentive significantly positively affected the volume of physicians’ PHKS directly with negative spillover to the duration of physicians’ PHKS. Moreover, the positive effect of incentives with higher difficulty on the volume of physicians’ PHKS was significantly smaller than that of incentives with low difficulty. Finally, professional title had a positive moderating effect on the volume of goal difficulty setting and did not significantly moderate the effect on the duration of physicians’ PHKS.Research limitations/implicationsSome limitations of this study are: firstly, because the field experiments were enterprise benefit oriented, the treatment and control groups were not balanced. Secondly, the experiments for different incentive measures were relatively similar, making it challenging to validate a causal effect. Finally, more consideration should be given to the strategy for setting hierarchical incentives in future research.Originality/valueThe research indicates that monetary incentives have a bilateral effect on PHKS, i.e. a positive direct effect on the volume of physicians’ contributions and a negative spillover effect on the duration of physicians’ PHKS. The professional titles of physicians also moderate such bilateral switches of PHKS. Furthermore, when a physician’s energy is limited, the goal difficulty setting of the incentive mechanism tends to be low. The more difficult the incentives are, the more inefficient the effects on physicians’ PHKS will be.

BACKGROUND Online health knowledge-sharing platforms (OHKSPs) play an increasingly important role in enriching residents’ health knowledge, thus improving their health behaviors. The participation of physicians determines whether the platforms can provide high-quality health knowledge to the public. However, little research has focused on motivating physicians to share more professional health knowledge on the platforms. Understanding physicians’ behavioral intention for professional health knowledge sharing (PHKS) is essential to support the development of OHKSPs and improve public health. OBJECTIVE We examine the relationship between incentives and PHKS in OHKSPs. Specifically, we explore the effects of incentives with different complexities in an OHKSP on the quantity and quality of PHKS. We explore how such effects differ across varying levels of professional titles. METHODS We conducted four field experiments with different incentive strategies in one of China's largest OHKSPs. Monthly panel data of 10,584 physicians were collected from January 2018 to December 2019. An empirical study with a fixed-effect analysis was conducted to test our hypotheses. The time fixed effect and the individual fixed effect were considered to identify incentives' effects on physicians’ PHKS. Additionally, a cross-sectional analysis was performed for a robustness check. RESULTS The results show that the incentive has a significant positive effect on the quantity of physicians’ PHKS (β=0.50012, 0.35167, 0.28337, 0.22899; p<0.01). However, the incentive has a significant negative effect on the quality of physicians’ PHKS (β=-0.12911, -0.12039, -0.10948, -0.07933; p<0.01). We found that the positive effect of incentives with high complexity on the quantity of physicians’ PHKS is significantly smaller than incentives with low complexity (0.22899<0.50012, p<0.01). The absolute value of the negative effect of incentives with high complexity on the quality of physicians’ PHKS is also significantly smaller than incentives with low complexity (-0.12911<-0.07933, p<0.01). Moreover, we found that high professional title positively impacts the effect of incentives with low complexity on both the quantity and the quality of physicians’ PHKS (coefficients are in the same valence). CONCLUSIONS Incentives have a bilateral effect on PHKS, i.e., a positive effect on the quantity of physicians’ contribution and a negative effect on the quality of physicians’ PHKS. Such bilateral switches of PHKS require a balanced state in conjunction with practical implications. Furthermore, the more complex the incentives are, the more inefficient the effects on physicians’ PHKS are. This research also identifies a moderate effect of professional titles on incentives and physicians’ PHKS.