This paper evaluates the Spanish open access (OA hereafter) mandate and its effects on Spanish research from 2014 to 2019. First, the degree of compliance with the mandate is studied. Then, classification trees and regression models are applied to determine the factors correlated with publishing in OA and the implications of OA types regarding the impact and visibility of academic articles. Results show that the compliance rate increased by 9% during the studied period, with a prevalence of gold and green OA routes. Moreover, the classification tree points towards the institutions’ nature and the research areas as the variables that better explain OA publishing. We argue that the institutions’ commitment to OA and the different availability of OA journals within research fields influence the decision to publish in OA. Last, we study how these practices affect research’s visibility and impact. We found that, in general, publishing in OA is beneficial for researchers, especially if they choose the green route. Further research at the faculty or departmental level might help discern the best strategies to encourage open-access publishing.

本文评估了西班牙开放获取（OA）指令及其对2014年至2019年西班牙研究的影响。首先，研究了该指令的遵守程度。然后，应用分类树和回归模型来确定与 OA 出版相关的因素以及 OA 类型对学术文章影响力和可见性的影响。结果显示，研究期间合规率提高了 9%，黄金和绿色 OA 路线盛行。此外，分类树将机构性质和研究领域作为更好地解释OA出版的变量。我们认为，机构对 OA 的承诺以及研究领域内 OA 期刊的不同可用性会影响以 OA 发表的决定。最后，我们研究这些实践如何影响研究的可见性和影响力。我们发现，总的来说，以开放获取方式发表对研究人员来说是有利的，特别是如果他们选择绿色途径的话。教师或部门层面的进一步研究可能有助于找出鼓励开放获取出版的最佳策略。