In this article, we measure and interpret the common “factors” that describe money market returns. Results are presented for both three‐and four‐factor models. We find that the three‐factor model explains, on average, 86 percent of the total variation in most money market returns while the four‐factor model explains, on average, 90 percent of this variation. Using mimicking portfolios, we provide an interpretation of the systematic risks represented by these factors.

In this article, the authors measure and interpret the common 'factors' that describe money market returns. Results are presented for both three- and four-factor models. The authors find that the three-factor model explains, on average, 86 percent of the total variation in most money market returns while the four-factor model explains, on average, 90 percent of this variation. Using mimicking portfolios, they provide an interpretation of the systematic risks represented by these factors.