Crowd-generated rating systems are ubiquitous on online platforms, yet little is known about their impact on investment decisions in crowdfunding. This study examines the introduction of a crowd-generated rating system on a leading South Korean platform that adopted ratings for equity crowdfunding while leaving reward crowdfunding unchanged. Using investment data and a difference-indifferences design, we identify the causal effects of ratings on investor behavior. We find that ratings increase funding frequency and amounts, accelerate investment timing, and reduce herding, with stronger effects among less experienced investors. Beyond the system's presence, we document participatory bias: investors who rate campaigns are significantly more likely to invest in them, and to invest earlier and in larger amounts. At the campaign level, ratings weaken the predictive power of conventional quality signals, suggesting that they substitute for traditional indicators. We also find that rating scores and evaluator volume indirectly improve startups' longer-term outcomes by increasing capital raised during crowdfunding. Overall, our findings demonstrate that crowd-generated ratings meaningfully shape investment behavior and campaign dynamics, providing an effective mechanism to support decision-making under uncertainty and information asymmetry.