For the last year, union leaders have tried to push Mayor Rahm Emanuel into focusing on other issues: smaller class sizes, more art and music programs and job security.
So far, the Republican National Convention keynote speeches have focused on jobs and the deficit. Something a little more surprising, maybe, has been the emphasis on teachers and schools.
There's no way to estimate the returns on a hug from your son or an afternoon of baking cookies with your brood, but the USDA was able to estimate how much a child takes out of your bank account.