If you throw all the products we buy and the services we use in one basket, then add up the price tag, that's the Gross Domestic Product, which is the primary metric economists use to assess the economic health of a country or region.

The easy part of calculating GDP is the calculation itself: C+I+G+(X-M)=GDP. Got it? No? Well, add Consumption, Investment by companies, Government purchases, and then take the product of eXports (calling it 'E' would lack sexiness) minus iMports ('I' was taken). Viola! GDP.

Still don't get it? Well, knowing the components helps. Consumption is the biggest component, and it's a tally of the cost of all the goods and services we buy. Investment is what companies spend on the real assets they own, plus the value of the inventory that we haven't gobbled up through consumption. Government purchases are what the Feds pay money for (whether it be highways or fighter jets, though big social programs, like welfare, aren't counted). And then we calculate the difference between the goods and services we¿re sending to other countries and the stuff we're bringing in.

Good. That explains it, except there's a catch. Inflation has a habit of distorting the numbers, so economists talk about either Nominal GDP or Real GDP. In fact, Real GDP isn't necessarily "real" for most folks, since it takes any inflation out. Nominal GDP includes the effects of inflation. (There's something called the implicit price deflator which is a calculation using the two, but we'll spare you the details.)

So, now that we know GDP, why do we want to? Well, it's good to compare different markets. And watching the trend shows whether a given economy is growing (good), stagnating (not so good), or shrinking (very not so good). When GDP goes down two quarters in a row, we're officially in a recession.

For the record, GDP is released at the end of each month, with most reporting ¿preliminary¿ data for the previous month. But you won't get final GDP numbers for the fourth quarter of a year until the very end of the first quarter of the next year. After all, it's not an easy number to calculate.