This is based on data from the State Demographer. For comparison purposes, I've indexed the number of households in each county to the base year of 1985.
The first graph shows us that Douglas County is not really in the same ballpark at the other metro counties. Since 1985, the number of households in Douglas County has increased by more than 700 percent. To be exact, the number of households in Douglas County increased 783 percent from 1985 to 2011.
This is a problem for the scale of our graph:
Obviously, Douglas County has seen more growth in households than any other metro county in Colorado. This is not surprising given that during the 1990s, Douglas County was one of the top ten fastest growing counties in the United States for multiple years.
In the second graph, I have removed Douglas County from the analysis to allow us to look at the other counties:
A few things stand out: Denver County has seen the smallest amount of growth, which is not surprising given that Denver has the least amount of room to grow. Significant growth did begin again back in 2006 as we started to see the effects of new development in Stapleton and the DIA area.
The areas with the largest growth (outside Douglas County) were in Larimer County and Weld County and El Paso County. The statewide curve is followed closely by Adams County and Arapahoe County, so those two counties appear to generally reflect the statewide trend. Mesa County saw some big growth from 2003-2008, but has flattened out quite a bit since 2008.