The year-on-year growth is calculated as (current - prior) / prior, but when the prior year is zero or negative, the calculation breaks. I see several rows where this happens, and the result is either infinity or nonsensical. Should we add a rule to exclude or flag such cases?

The formula for the growth rate divides by the prior-year value, but when prior values are missing (coded as null), the calculation becomes null, which propagates the missing-data problem forward. Over time, a string of missing values can silence an entire region. Should we implement a forward-fill or interpolation strategy for missing values?