Create an "other" category

If we want to summarize Evanston 311 requests by zip code, it would be useful to group all of the low frequency zip codes together in an "other" category.

Which of the following values, when substituted for ??? in the query, would give the result below?

Query:

SELECT CASE WHEN zipcount < ??? THEN 'other'
       ELSE zip
       END AS zip_recoded,
       sum(zipcount) AS zipsum
  FROM (SELECT zip, count(*) AS zipcount
          FROM evanston311
         GROUP BY zip) AS fullcounts
 GROUP BY zip_recoded
 ORDER BY zipsum DESC;

Result:

zip_recoded    zipsum
60201          19054
60202          11165
null           5528
other          429
60208          255