user: Question: What is the average Density of 53 No. munic.?
Columns: ['Abbr', 'Canton', 'Capital', 'Density (per km²)', 'No. munic.', 's Official language']
Types: ['text', 'text', 'text', 'real', 'real', 'text']
Sample row: ['ZH', 'Zurich', 'Zurich', 701.0, 171.0, 'German']
SQL:

assistant: SELECT AVG("Density (per km²)") FROM "Table" WHERE "No. munic." = 53.0;