BEA publishes estimates of levels at annual rates (for most series) for ease of comparisons with related and historical data . For example, in its February 2, 2004 personal income and outlays release, BEA estimated that personal income for December 2003 was $9,335.8 billion at an annual rate. This is easily compared to BEA’s estimates of personal income for the fourth quarter of 2003 ($9,312.6 billion, at an annual rate) and for the entire year of 2003 ($9,187.4 billion). The level of personal income in December at a monthly rate is $778.0 billion -- derived by dividing the annual rate estimate by 12. Fourth-quarter personal income at a quarterly rate is $2,328.2 billions -- derived by dividing the annual rate estimate by 4. As you can see, comparing these estimates with each other and with the 2003 annual estimates is more difficult than the comparisons when all three estimates are at annual rates.