The BLS uses surveys and the surveys are getting declining response rates.
ADP uses actual data from nearly 20% of the US private sector and then uses a multiplier. In 2022, it hired a Stanford Uiv. lab and changed its multiplier based on their more rigorous methods.
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Per CNN (Dec 2023):
One of the biggest issues the BLS suffers from is falling response rates to their surveys, which reduces the accuracy of their reports, said Erica Groshen, a former commissioner of the Bureau of Labor Statistics who is now at Cornell University.
Per Grok:
ADP uses actual payroll data from over 25 million employees across its client base, adjusted for seasonality and weighted to reflect national trends. . . . (covering about 20% of private-sector employees) . . .
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In 2022, ADP retooled its National Employment Report in collaboration with the Stanford Digital Economy Lab, moving away from forecasting the BLS report to creating an independent, real-time measure of private-sector employment based on actual payroll data. This change explicitly reduced its focus on predicting BLS numbers, leading to larger discrepancies.
BLS takes a voluntary survey —> Then uses a multiplier.
ADP uses actual data —> Then uses a multiplier.
In the past both used the same (or nearly the same) multiplier.
A growing bodyof evidence suggested that multiplier was outdated
so in 2022 ADP swiched to the newer better multplier (they made the switch by contrcting with Stanford Univ.)
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From time to time things like mutlipliers need to be changed, but the changes don’t come very often because:
Any time they are changed, the change makes it diffcult/impossible to compare new data with old.
Often, when changes are made, people allege the changes are part of a cover-up “cooking the books.”