Critical Reasoning (CR) | Re: The National Association of Fire Fighters says that 45

The National Association of Fire Fighters says that 45 percent of homes now have smoke detectors, whereas only 30 percent of homes had them 10 years ago. This makes early detection of house fires no more likely, however, because over half of the domestic smoke detectors are either without batteries or else inoperative for some other reason.

The conclusion is that smoke detectors are still not effective despite the increase in their prevalence because many of them don't function (due to lack of batteries or other issue).