Analyze + Index

Hi,

Say I have a table of 3000 user's,
Before I insert another user I need to check if that user is already in 
there, so I have a 3 column index on a table ( phone,lastname,firstname ).

First I check for the user using the index if they are not in there I 
then add an new user so I now have 3001.
For my next user I then check again using the same procedure.

Is the following correct ?

As I have not yet Analyzed the db my index is still 3000 rows and my 
user table is 3001.
If I add another user my index is still 3000 and my table 3002.

So I either analyze after each insert or use a seqential scan.

I wonder this as I have a csv file of users to bulk insert each day.
Typically I'll have a file of 1500 or so  users to add or append data to.

Thanks.