SQLITE strftime() function issue

SELECT strftime('%W', 'Week'), sum(income) FROM tableOne GROUP BY Week;

Format for date is a simple date: YYYY-MM-DD

PROBLEM: When run no value for the Week column is provided. Any suggestions?

There is data in the table and when the query is run the income is summarized by the date in the week column. Thing is, this column contains a date that may be any day of the week and often multiple different days of the same week. I need to summarize the income by week.