During the nineteenth century, why was it difficult for census officers to collect figures on mortality and diseases?

All deaths were not registered, and illness was not always reported, nor treated by licensed doctors.

The correct answer is Option 2 - All deaths were not registered, and illness was not always reported, nor treated by licensed doctors.

Colonial rule was based on the production of enormous amounts of data. The British kept detailed records of their trading activities in order to regulate their commercial affairs. To keep track of life in the growing cities, they carried out regular surveys, gathered statistical data, and published various official reports.

The census operation, for instance, was a means by which social data were converted into convenient statistics about the population.

Often people themselves refused to cooperate or gave evasive answers to the census officials. For a long while they were suspicious of census operations and believed that enquiries were being conducted to impose new taxes. Upper-caste people were also unwilling to give any information regarding the women of their household: women were supposed to be secluded within the interior of the household and not subjected to public gaze or public enquiry.

Census officials also found that people were claiming identities that they associated with higher status.  Similarly, the figures of mortality and disease were difficult to collect, for all deaths were not registered, and illness was not always reported, nor treated by licensed doctors. Thus historians have to use sources like the census with great caution, keeping in mind their possible biases, recalculating figures and understanding what the figures do not tell.