Fun with Graphs and Rosaries

"WM Hiker Runner" requested that I discuss this graph from a previous post/CARA.  Now that semesters and weddings are over, and since I haven't received coursework in the mail yet, I have time!

The graph summarizes the interaction of Catholics with particular bits of material culture.  The Catholics surveyed are divided into two groups: all Catholics and weekly Mass-goers.  I found the highest and lowest disparities of particular interest:  weekly Mass goers are twice as likely to carry a rosary (there is a 22 percentage point difference).  The difference in cross-wearing is smaller: only seven percentage points and nowhere near twice as likely.  Mass attendance, of course, is not the cause of the rosary-carrying, but the correlations makes sense.  Both are strongly related to a specifically Catholic spiritual identity.  Wearing a cross is not necessarily so: it is Christian, but not exclusively Catholic.  Along the same lines, crosses are made to be worn, rosaries prayed.

I would love to continue a study like this.  Who wears crosses and carries (or wears) rosaries?  What is the reasoning?  Is it a personal reminder or a way of identifying oneself to others?  How does this vary based on the type of material object: rosary, prayer card, saint medal, cross?  Maybe someone has already done this study and I just need to find it.