* Field of study: Some fields have much higher completion rates than others. Fields like STEM (Science, Technology, Engineering, and Mathematics) often have higher completion rates than humanities or social sciences.
* Institution type: Graduation rates differ between public and private universities, and also between research-intensive universities and smaller institutions.
* Student demographics: Factors like socioeconomic status, prior academic performance, and access to resources can impact graduation rates.
* Definition of "graduate": The definition of "graduation" can vary. Does it include students who complete a master's degree or only those who complete a doctoral degree?
While some studies exist on graduate student completion rates, they often focus on specific institutions, fields, or student populations. A general percentage would be misleading and inaccurate. To find a relevant statistic, you'd need to specify the parameters you're interested in (e.g., "What is the PhD graduation rate in engineering at public universities in the US?").