By the turn of the 20th century, back-to-back houses had become unpopular with residents and the government, who sought to ban their construction and eradicate existing properties nationwide. Among the primary concerns cited were health and ventilation, as statistics were revealing that residents of back-to-back houses suffered from relatively poor health. In Manchester, Dr James Niven noted that mortality rates among those living in back-to-back houses exceeded those from through-houses by 40 per cent, along with an increased incidence of infectious diseases and diarrhoea. A change in the law in 1909 forbade the erection of this style of house.