On April 2, 2012, I'll be able to find out how much money my Grandpa Theodore Schwartz made in 1939. Why do I care? Because Grandpa ran a grocery store and, according to family stories, he was too soft-hearted to take money from customers who were hungry but couldn't pay for their purchases. In eight months, I'll know whether Grandpa's income was suffering or whether he and Grandma Minnie Farkas Schwartz had enough money to get by.
Yearly income in 1939 is only one of the important questions that any beginning genealogist should be thrilled to see on the 1940 Census form.
Another key question is "Residence, April 1, 1935." If you've already checked your ancestors' whereabouts in the 1930 Census, you'll now know where they were at the beginning, middle, and end of the Depression.
There's only one catch, and that's the biggest tip of all for using the 1940 Census: The names won't be indexed, at least not at first. You should start now to assemble a list of the exact addresses of all the relatives you're looking for in the 1940 Census. Second task: Locate the exact Enumeration District for each, which can be harder than it sounds (alas).** But if you start soon, you'll be ready.
When the Census records are opened in 2012, my fingers will be poised over the keyboard, ready to find out about Grandpa's income and his housing situation in the 1930s. How about you?
For more info, see the Census page at Archives.com.
** JoelWeintraub's comment, below, has this excellent idea: "I suggest your readers start by taking our tutorial at: http://stevemorse.org/census/quiz.php." Thanks, Joel!