Gross domestic product (GDP) is the broadest measure of aggregate economic activity and encompasses every sector of the economy. The monthly report is based on output data only as the income and expenditure series are not available.

GDP covers all aspects of economic activity. Investors need to closely track the economy because it usually dictates how investments will perform. Stock market investors like to see healthy economic growth because robust business activity translates to higher corporate profits. GDP contains a treasure-trove of information which not only paints an image of the overall economy, but tells investors about important trends within the big picture. However, the monthly report is quite limited and only provides data on the main output sectors. More detailed information is available in the quarterly reports.