Why did the percentage of population living in poverty decrease?

In the famous Breadline Britain study in 1985, researchers Mack and Lansely asked a sample of the whole population what they considered essential needs for living. A deprivation index was formed, including things such as a damp free home and outings for children, and it was found that 7.5 million people or over 10% of the population was living in poverty in the UK.
A few years earlier research had been carried out by Peter Townsend on poverty in the UK through calculation of the total costs of life necessities in that particular society.
Mack and Lansely found that a smaller percentage of the population was living in poverty at the time of their own research.
What could be some reasons for this?