What is a 'ghost mall' and how many 'ghost malls' are there in India?

According to international property consultant Knight Frank, if a mall has a vacancy of more than 40%, it's considered as a 'ghost mall'. As per its report 'Think India, Think Retail 2022', 57 of the 271 operational malls in top eight cities - Ahmedabad, Bengaluru, Chennai, Hyderabad, Kolkata, Mumbai, National Capital Region (NCR) and Pune are in a dilapidated state.