I'm working on some financial analysis code which I'd like to test against a historical dataseries to analyze the correlations to my algorithm to some non-finance related data. Ideally, I'd like to test against a dataseries which provides a monthly float value as far back as 1997. Maybe it's the temperature somewhere on the 1st of the month. Maybe its the number of traffic accidents on the 1st day of each month in a city. Basically, just something somewhat random, but with the monthly value to test against.
Can anybody think of a publicly-available data-series which might have a monthly point of data as far back as 1997. A link to the data-source would be even better.