Question on re-indexing data for graphing A file contains data for 1975-2012 of housing prices across a panel of countries. 
However, it's indexed to 2005, so each country's housing price series converges to 100 in  2005, then they spread apart again to 2012.
This makes graphing all data series on one chart for comparison's sake unintelligible. 
Without the original data, could one properly reindex the data from 1975 in a statistically correct manner, and how could someone do this in either R or excel?
 A: You can do this really easily.  Let's take an example.
Index values:
Country A: 1975 = 30; 2005 = 100;
Country B: 1975 = 50; 2005 = 100.
What you need to do is re-index that series so that 1975 = 100.
So, now you have the following indexed values:
Country A: 1975 = 100; 2005 = 100/30 = 333;
Country B: 1975 = 100; 2005 = 100/50 = 200.
As shown, country A home prices have more than trebled between 1975 and 2005.  And, country B have just doubled.  
You can construct every year data point using the exact same arithmetic.  And, this way you will be able to readily compare home price appreciation trends across countries.  
Mind you, the 2005 = 100 index was not totally absent of meaning.  Well maybe a more appropriate year would have been 2006 or 2007 that captured the peak of home prices in many countries before the worldwide housing bubble burst.  And, this way you can observe across countries how rapidly home price increased before the peak and how quickly they crashed after it.  
It really all depends on what you want to focus on.  For my two bits, I think an index anchored around 2006 or 2007 could be really informative for the mentioned reasons. 
