CREATE TABLE table_24627 ("Year" FLOAT, "Starts" FLOAT, "Wins" FLOAT, "Top 5" FLOAT, "Top 10" FLOAT, "Poles" FLOAT, "Avg. Start" TEXT, "Avg. Finish" TEXT, "Winnings" TEXT, "Position" TEXT, "Team ( s ) " TEXT)

Name the number of years for 18.5
SELECT COUNT("Year") FROM table_24627 WHERE "Avg. Finish" = '18.5'
SELECT COUNT("Year") FROM "table_24627" WHERE "Avg. Finish" = '18.5'