Solve the following sql problem:
How many times more for the number of users who took the "mental health survey for 2017" than "mental health survey for 2018"?

Schema:
SCHEMA:
- Table: Question
  - Column: questiontext
    - Samples: [What is your age?, What is your gender?, What country do you live in?, If you live in the United States, which state or territory do you live..., Are you self-employed? (truncated)]
  - Column: questionid
    - Samples: [1, 2, 3, 4, 5]
- Table: Survey
  - Column: SurveyID
    - Samples: [2014, 2016, 2017, 2018, 2019]
  - Column: Description
    - Samples: [mental health survey for 2014, mental health survey for 2016, mental health survey for 2017, mental health survey for 2018, mental health survey for 2019]
- Table: Answer
  - Column: AnswerText
    - Samples: [37, 44, 32, 31, 31]
  - Column: SurveyID
    - Samples: [2014, 2014, 2014, 2014, 2014]
  - Column: UserID
    - Samples: [1, 2, 3, 4, 5]
  - Column: QuestionID
    - Samples: [1, 1, 1, 1, 1]

SELECT CAST(COUNT(T1.UserID) AS REAL) / ( SELECT COUNT(T1.UserID) FROM Answer AS T1 INNER JOIN Survey AS T2 ON T1.SurveyID = T2.SurveyID WHERE T2.Description = 'mental health survey for 2018' ) FROM Answer AS T1 INNER JOIN Survey AS T2 ON T1.SurveyID = T2.SurveyID WHERE T2.Description = 'mental health survey for 2017'