Nearly half of the white population only meet people from a different ethnic background when being served in shops or restaurants, according to the latest happiness index study published by the Office for National Statistics (ONS).

Meanwhile, one in 20 adults describe themselves as "completely lonely" in their everyday lives, and adults are more likely to be happy with their personal relationships than with their lives in general.

The study is part of the ONS's happiness index programme, a £2m-a-year wellbeing project announced by the prime minister, David Cameron, in 2010 to try to create an alternative to gross domestic product as a national measurement. The ONS has been asking people how content they feel as part of its integrated household survey of 200,000 people.

In December last year, the first results were published, which showed that three quarters of Britons rated their own life satisfaction with a score of seven or more out of 10. Similar proportions also rated the things they do in life as worthwhile and their happiness over the previous day at seven or more out of 10.

The figures published on Tuesday, which collect different survey results together, confirm what most of us may have suspected all along: if you are happier in your personal relationship, you will be happier in your life.

Fewer than half of adults over 16 – 42% – get to spend time every day with their families, and those who are not divorced or separated are happier than those who are.

The ethnicity figures show that despite Britain becoming a more diverse society, many people only meet others of the same ethnicity. The least mixing appears to take place at school or nursery – only 15% of white people meet other races there, and only a third of other groups.

The older you are, the less likely you are to mix too – 52% of over-75s say they mix with other ethnicities, the lowest of any age group. By contrast, the greatest amount of mixing takes place with young people: 92% of 16- to 24-year-olds say they regularly mix with other ethnicities, mostly in pubs and nightclubs.

The results also show the growing importance of friends to Britons. In 2011, 42% of adults say they spent time most days or every day with their friends, and nine out of 10 say they are highly satisfied with those relationships, with higher rates among the young than the old.