The Bureau of Labor Statistics (BLS) provides two major monthly indicators of employment dynamics: the monthly employment change from the Current Employment Statistics (CES) survey and monthly hires and separations data from the new Job Openings and Labor Turnover Survey (JOLTS). On a conceptual basis, one would expect that the over-the-month difference in hires minus separations would equal employment change for an establishment. However, there are a number of concept, reference period, and employer payroll practice issues that impact this relationship. This paper looks at the difficulty in measuring monthly hires and separations and the methodology that BLS put in place to control for expected differences from employment data. Measures of the magnitude and seasonal nature of the differences will be presented along with what is currently known about the causes of these differences. The paper will conclude with a discussion of future research plans.