- Date: type `Date`. 
- TickerLast: type `chr`. The ticker as of December 2015 
- Ticker: type `chr`. Monthly ticker
 period 
- Company: type `chr`. The name of company with TickerLast 
- CapGroupLast: type `chr`. Company market capitalization group
 as of December 2015, one of: MicroCap, SmallCap, MidCap or LargeCap 
- CapGroup: type `chr`. Monthly market capitalization group 
- GICS: type `chr`. 6 digit S&P GICS code 
- Sector: type `chr`. One of 10 sectors specified by the first
 two digits of the GICS code 
- Return: type `num`. Arithmetic stock return from one period
 to the next in decimal form 
- RetExDiv: type `num`. 
- Price: type `num`. Stock price at each time period in decimal
 form 
- PrcSplitAdj: type `num`. 
- Ret4WkBill: type `num`. Return of 4 week Treasury bill 
- Ret13WkBill: type `num`. Return of 13 week Treasury bill 
- Ret1YrBill: type `num`. Return of 1 year Treasury bill 
- mktIndexCRSP: type `num`. CRSP value weighted market return