user: Question: What was the total number of years than had Best Improved Singer (躍進歌手)?
Columns: ['Year', 'Award', 'Category', 'Nomination', 'Result']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [2007.0, 'Metro Radio Hit Awards', 'Best Overseas New Artist', 'Danson Tang', 'Won']
SQL:

assistant: SELECT SUM("Year") FROM "Table" WHERE "Category" = 'Best Improved Singer (躍進歌手)';