Database: books
Question: In books authored by Abraham Lincoln, what is the percentage of the books published in 1992?
SQL: SELECT CAST(SUM(CASE WHEN STRFTIME('%Y', T1.publication_date) = '1992' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(*) FROM book AS T1 INNER JOIN book_author AS T2 ON T1.book_id = T2.book_id INNER JOIN author AS T3 ON T3.author_id = T2.author_id WHERE T3.author_name = 'Abraham Lincoln'