‘How many people do you employ this month?” might sound like the kind of question an employer can easily answer, but it’s not. Especially for large businesses, the exact number of employees in a given month is hard to pin down. The media report layoffs and hires in round numbers, but for calculating total employment in the country, it really matters whether “500” means 478 or 523, because those discrepancies multiplied across millions of businesses make a huge difference. Within government, Donald Trump’s appointee as BLS commissioner, William Beach, has been a leader in calling for modernizing the surveys that...