The research says 22% of sun-like stars have Earth-like planets in their habitable zone. Seems like they're all based on different assumptions of the number of

The research says 22% of sun-like stars have Earth-like planets in their habitable zone. Seems like they're all based on different assumptions of the number of sun-like stars. >Guardian: There are around 100bn stars in our galaxy, of which 10% are like the sun. >ABC: There are about 200 billion stars in our galaxy, with 40 billion of them like our sun, Marcy said. One of his co-authors put the number of sun-like stars closer to 50 billion, meaning there would be at least 11 billion planets like ours. >Kurzweil: The estimate was based on a statistical analysis of all the Kepler observations of NASA’s Kepler space telescope of the 200 billion stars in our galaxy. Given that about 20 percent of stars are Sun-like, the researchers say, that amounts to several tens of billions of potentially habitable, Earth-size planets in the Milky Way Galaxy. n.b. Kurzweil's math clearly sums up to 8.8. Maybe he's adding in stars unlike the Sun and not mentioning it (given that the article discussed is based on earlier work showing 15% of red dwarfs have Earth-like planets in the habitable zone: http://www.nytimes.com/2013/11/05/science/cosmic-census-finds-billions-of-planets-that-could-be-like-earth.html?ref=science&_r=0 http://www.nytimes.com/2013/11/05/science/cosmic-census-find... ).