The College Board has data on the trends of college costs. You can find a spreadsheet with lots of tables and figures here. I’m going to look at just the annual cost increases for tuition, fees and room and board for public 4 year colleges.
Currently the average cost of a year of tuition and room and board plus fees at a 4 year public college is $15,213 for the 2009-2010 school year. The cost of public college has tripled since 1980. The average annual increase is 6.5%.
First take a look at a chart showing the annual percent change in the cost of college from 1980 to 2010:
The maximum annual increase was for the 1981-1982 year when costs went up 12.5%. But back then inflation was pretty rampant. The smallest change as an increase of 1.9% in 1995-1996.
Now lets look at the figures if adjusted for inflation:
If you take inflation into account then the average annual change was +2.7%. The worst year is the 2009-2010 year when college costs went up 8.2% above inflation. There are a few years when costs went down relative to inflation and the 1980-1981 year was the largest decline at -3.1%.
College costs are a bit volatile. As you can see in the charts the increases bounce up and down. I can only guess why its so inconsistent, but it may be due to things like government policy changes or reactions to economic conditions. Over the long term public college costs have increased at a pace around double the rate of inflation for the past 3 decades.
It should be kept in mind that most people get some form of scholarships or need based financial aid so looking at the 'retail sticker price' for college without considering aid doesn't give us the full picture.
Note that this information is specific to public 4 year colleges and trends for private colleges, 2 year schools (community college or junior college) or cost for online schools is going to be a bit different. Though in general college costs have been rising in fairly similar patterns for any kind of college.