I was warned that using two consecutive years of MORG data from NBER would result in double-counting of households because of the nature of the rotation and the fact that the MORG extracts contain all months in a year. Is it correct that when I use IPUMS online analysis (SDA) and select ORG data, there is no such problem because it is only the month of March provided for each year? So can I build up my sample size by combining several years of ORG data on the online analysis without any (double-counting) problem?

# When doing an online analysis can I combine several years of ORG data to build up my sample size?

The online analysis system in IPUMS CPS only allows for analysis using the ASEC samples. Therefore, individuals can be in this combined set of samples up to two times. If you restrict your sample to only those in the outgoing rotation group (i.e., the observation has MISH 4 or 8), then individuals could still be included in the combined sample twice. For example, if an individual has MISH==4 in March of a given year, then they will have MISH==8 in March of the next year. This is because the CPS follows a 4-8-4 sampling design where individuals are included in the sample for 4 months, excluded for 8, and then included again for 4 more months. So, in order to prevent double-counting of individuals, youâ€™ll want to restrict your sample to either only MISH==4 or MISH==8.