* Variations in record-keeping: Record-keeping practices have changed drastically over Ford's more than 100-year history.
* Global sales: Tracking sales across all markets and regions worldwide would be a massive undertaking.
* Defining "car": The definition of a "car" itself has evolved. Should this include trucks, SUVs, and other vehicles Ford produces?
While you can find yearly sales figures and overall production numbers, a precise total for all time is not available.