You can make a chart out of the gold/silver ratio, and it may be neat to look at. But, I don't think you'll be able to make a conclusion from all of it. Many times, other than economic instability, the two often head in opposite directions. Sometimes it's a supply issue. Sometimes there are only opinions on why they are doing what they are doing.
This is more about where we have been and where we may be heading towards, the chart is just a history. Its something to look back on to see how it does not matter what century we are in, the economy is never stable for extended periods of times. This is evident from the chart. The only exception was in between 1900-1920 for some reason.
http://www.irs.gov/Businesses/Small-Businesses-&-Self-Employed/Form-8300-and-Reporting-Cash-Payments-of-Over-$10,000 the above is the link...I didn't make it up