z. betty: but the success wasn't just due to bigger and better ships aimed at a ballooning population of american middle class. by registering ships under foreign flags, like liberia or panama, companies avoided u.s. labor laws and environmental and tax regulations that regular land-based tourism were forced to follow. between 1970 and 2014, the cruise industry's passenger load grew more than 4000%, from 500,000 to more than 21 million cruisers each year. but the industry's environmental practices and working conditions have drawn a lot of scrutiny in decades past. and in the last several years, the industry has been plagued with a series of incidents that have hit the headlines and scared passengers and public alike. >> sick at sea. a royal caribbean cruise forced to turn back when 200 people on board get the norovirus. betty: from norovirus outbreaks on eight separate cruises last year >> nightmare on a carnival cruise ship -- betty: -- to an ebola scare that created panic. on a carnival magic cruiseship. >> we knew something bad was happening. betty: to the devastating crash of the co