I had asked him this very question without any foreknowledge of this discussion topic here. But I do have the info in front of me from II called the TRAVEL DEMAND INDEX. If I understand the chart correctly it gives a rating based on hotel projections which are based on demand and relative room rates. It assigns the average demand FOR THAT AREA as 100 and works from there. A rating above 100 is above average. In addition, II overlays their "peak exchange periods" on this grid.
Here's the one in the old II book . The new book actually gives almost all weeks in CO a 5 point LOWER rating than this chart shows. In addition, The "Peak Exchange Period" for the new book does not include weeks 2-5, 34, 35 or 52. The numbers for Utah or Idaho, etc; do not show a similar reduced demand.
One thing to note is that 100 in CO is not the same as 100 in Orlando, they are all relative for the area involved. Another way to get info would be to look at rentals rates from management companies for the various areas, that info shouldn't be hard to find. I thought you might enjoy seeing some visuals to illustrate the info.
Note that in general, December outside Xmas and January tend to be far slower months than Feb and March. This is true for HI, FL, Aruba, Cancun, HH, Williamsburg, Branson, DLP, Gatlinburg; just as some I have a direct idea about. But it is relative as HI is harder to get than Branson or Orlando. I'm sure the reason is that people are just past Xmas and tend to travel more in Feb and March. The point about Jan being a good time to go is exactly the point my friend was making. He said he goes during Jan because rental rates are low but the skiing is fine. He said he couldn't afford to use it when the rates were high as that's essentially how he pays for it.