本文

Dear all, Imai-san, and Asakawa-san.

Thank you for your reply for the garbage e-mail.  Both of your view are 
interesting for me...  

>
怪我をなされたり、盗難に遭われたりと、このところついてないみたいですね。
> お気をつけ下さい。
Thank you for your kind words.
 
> なかなか面白い調査ですね。調査時点はいつ頃です
1994.  It is conducted every year.  And the topics are changed nearly
every year.

We can use micro-data of this survey in many countries, including Japan.
Although Japanese statistical law strictly prohibits the disclosure of 
micro-data, this data can be used in many countries, I think.  It was
conducted by NHK and sample size are very very small, say 1500. 
Despite such
a small sample size, I need to use it because there is no other
accessible Japanese
micro-data.
 
As IMAI-san pointed out, I did not consider missing data.
It would be different from those results if missing data are included.