One of my students reported that return for AAPL between April 30, 2014 and June 30, 2014 was different than what was shown in my class notes which were prepared in early 2016. I investigated the error and found the problem in incorrectly coded dividends. The screenshot below shows the problem dividends:

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This makes me wonder how many such errors are there in Yahoo! Finance data and how reliable are the results using data downloaded using the getsymbols function in R. Has anyone else experienced similar issues?



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