Trend growth in the labor force is a key determinant of trends in employment and gross domestic product (GDP). Forecasts by Macroeconomic Advisers (MA) have long anticipated a marked slowing in trend growth of the labor force that would contribute to a slowing in potential GDP growth. This is reflected in MA’s forecast that the aggregate rate of labor force participation will trend down, especially after 2010, largely in response to the aging of the baby boom generation, whose members are beginning to approach typical retirement ages. Expectations for a downward trajectory for the participation rate and a slowing in trend labor force growth are not unique. However, this article reports on MA research suggesting that the opposite is possible: that the slowdown in trend labor force growth could be relatively modest and that the trend in the aggregate rate of labor force participation will decline little, if at all, over the next decade.