Trends on time spent studying over the the past few decades, for students outside the US Is there any research/study/survey/dataset that looked at the trends on the time students spent on studying, over the the past few decades in different countries in the world (aside from the USA)?

I am mostly interested in the field of computer science, if field-specific, and college level, if level-specific.
For Germany the data is there in the form of the "Studierenden survey", which exists since 1982. However, I don't know if it is analysed. The datasets are available, so I added a list of links to the datasets for the different years in case you want to do the analysis yourself.

2012/13: http://dx.doi.org/10.4232/1.5126 

2009/10: http://dx.doi.org/10.4232/1.11059 

2006/07: http://dx.doi.org/10.4232/1.4263

2003/04: http://dx.doi.org/10.4232/1.4344

2000/01: http://dx.doi.org/10.4232/1.4208

1997/98: http://dx.doi.org/10.4232/1.3511 

1994/95: http://dx.doi.org/10.4232/1.3131 

1992/93: http://dx.doi.org/10.4232/1.3130

1989/90: http://dx.doi.org/10.4232/1.2417

1986/87: http://dx.doi.org/10.4232/1.2416

1984/85: http://dx.doi.org/10.4232/1.1885

1982/83: http://dx.doi.org/10.4232/1.1884