CPS geographic population threshold

What is the minimum population threshold for the lowest geographic level available in the CPS?

The lowest level geography available in IPUMS CPS is the METARA and the minimum size is 100,000. Also note, however, that the Census Bureau warns, “Although estimates for the larger areas such as New York, Los Angeles, and so forth, should be fairly accurate and valid for a multitude of uses, estimates for the smaller metropolitan areas (those with populations under 500,000) should be used with caution because of the relatively large sampling variability associated with these estimates.”