Step 1: Son preference and female foeticide:
Deep-rooted patriarchal son-preference, linked to lineage continuation, property inheritance and dowry-related economic burden, has led to the misuse of prenatal sex-determination technology for female foeticide, directly skewing the sex ratio at birth.
Step 2: Neglect of the girl child:
Even after birth, unequal access to nutrition, healthcare and education for girls compared to boys raises female infant and child mortality, further depressing the ratio.
Step 3: Social and economic factors:
Dowry practices, perception of daughters as an economic "liability", and lower social value attached to women's labour reinforce these preferences across regions and classes.
Final Answer:
The declining sex ratio results mainly from patriarchal son-preference leading to female foeticide, neglect of girl children's health and nutrition, and dowry-linked economic attitudes toward daughters.