Half of the papers I graded today were plagiarized. (I have now finished one class. The ration was 2:3, with original papers winning.) Some took whole paragraphs from one source and attributed them to another, so that I wouldn’t notice the plagiarism. Some cited the sources used, but did not put the quotes in quotation marks.
I am afraid that I may have missed a few plagiarized papers on the last research paper because I did not spot check them all. (Spot checking is where I put in two or three of the most advanced sentences in the paper and see if it comes up on Google. Unfortunately many of them have.)
I am still working. This is depressing though.