Spillover Effects of Paid Functions on Physicians' Unpaid Knowledge Activities: Quasi-Experimental Approach

To promote sustained contributions by physicians to online health care communities, these platforms have introduced a content payment model that offers economic incentives for physicians' online knowledge activities. However, the impact of these paid features on unpaid knowledge activities remains unexplored.

This study investigated how the introduction of economic incentives in online medical communities affects physicians' unpaid knowledge activities in the community.

The data for this study were obtained from the Haodf Online platform in China, which has implemented paid scenarios for its science popularization function, providing economic benefits to physicians. The dataset, which comprises panel data, includes 7453 physicians who participated in both paid and unpaid knowledge contributions on the website. This study examined the impact of paid knowledge activities on physicians' free knowledge contributions, focusing on dimensions including knowledge quantity, quality, and diversity. To address the timing discrepancies in physicians' participation in paid activities, we used a quasi-experimental design that combined the approach of propensity score matching and multi-period difference in differences.

In the balance test results of the propensity score matching, the absolute values of the SDs of all matching variables were mostly <5% after matching, ensuring the accuracy of the results obtained from the difference in differences method. This study found that participation in paid knowledge activities had a positive spillover effect on physicians' free knowledge contributions, which manifested in the increase in post quantity (473.1%; P<.001), article length (108%; P=.009), function word frequency (0.6%; P=.001), causal word frequency (0.2%; P<.001), and content information entropy (6.6%; P=.006). The paid function led to a decrease in the consistency between titles and content (-115.5%; P<.001).

The findings of this study contribute to the existing literature on the impact of economic incentives in the medical context. For the platform, providing economic incentives to physicians can have positive significance in promoting the development of the platform's knowledge ecosystem and can effectively encourage physicians to contribute to both paid and free knowledge activities. This study provides a valuable reference for the platform to introduce a paid knowledge model, which is beneficial to the sustainable development of the platform.