context: British researchers Richard G. Wilkinson and Kate Pickett have found higher rates of health and social problems (obesity, mental illness, homicides, teenage births, incarceration, child conflict, drug use), and lower rates of social goods (life expectancy by country, educational performance, trust among strangers, women's status, social mobility, even numbers of patents issued) in countries and states with higher inequality. Using statistics from 23 developed countries and the 50 states of the US, they found social/health problems lower in countries like Japan and Finland and states like Utah and New Hampshire with high levels of equality, than in countries (US and UK) and states (Mississippi and New York) with large differences in household income.
question: ব্রিটিশ গবেষকরা কতগুলো উন্নত দেশ থেকে পরিসংখ্যান সংগ্রহ করেছিলেন?
answers: 23 23 23