Most of us reading (or writing) Grandma's Briefs are grandparents. Which means most of us here know how much money grandparents spend on their grandchildren, their parents, their children and, when there's a smidgen left, on ourselves.

Interestingly, marketers don't seem to know how much we grandparents spend on ourselves and our loved ones. Or so it seems. Perhaps they do know—some brands clearly do—though they have yet to figure out how to effectively reach us with messages on the services and products we want to see, want to use, want to buy.

grandparent economy book Author Lori K. Bitter lends them a hand in her new book on the topic, The Grandparent Economy: How Baby Boomers Are Bridging the Generation Gap ($34.95, Paramount Market Publishing), which I recently received free for review.

The 138-page primer on engaging the 65 million grandparents in the United States is a must-read for marketers. And, thanks to all the graphs and stats and tidbits Bitter provides on...

• The majority of today’s grandparents—53% of grandmothers and 54% of grandfathers—are Baby Boomers under age 65.

• The average age of becoming a grandparent in the United States is 48.

• There were an estimated 65 million grandmothers and grandfathers in 2010. By 2020, they are projected to reach 80 million, at which time they will be nearly one-in-three adults.

• The number of grandparents is growing at twice the overall population growth rate.

• A majority of those with grandchildren are women, in part because on average women age 45+ live approximately seven years longer than men. At the time the 2010 Census was conducted, there were about 124 grandmothers for every 100 grandfathers.

• Today’s grandparents are more likely to be college graduates (37%) and fully employed than at any time in the past.

• The grandparent-age share of the nation's income is 60%.

• The mean annual income of grandparent-age households was $68,500—about $500 above the mean income for all U.S. households. Among all grandparent-age households, about one-in-four had an annual income of $90,000 or more.

• They spend$52 billion a year on their grandkids.

• There are an estimated 4.5 million grandparentheaded households that include one or more of their grandchildren. That means approximately one in every nine (11%) grandparent households includes at least one grandchild.

• Three-quarters of grandparents are online. Forty-five percent are on social networks, and six percent have started a blog.

• 70 percent of grandparents see their grandchildren at least once a week.

• Forty-three percent exercise or play sports.

• Thirty-eight percent report having sex at least twice a week.

• Ten percent have a tattoo.

Sources: US Census Bureau, MetLife Mature Market Institute, Grandparents.com

Today's question:

What on the list surprises you...and what would you like to add?

This post also published as a guest post on Family Home and Life.