Here's a table of the number of category 4 or 5 Atlantic hurricanes broken down by year range. Note that the first two rows are 50 year ranges, the next two are 25 year ranges, and the last is 18 years, so the import columns are the rate columns, which give the average number of storms per year of each category during the corresponding year range:

   Years     Cat 4     Cat 5     4 or 5
            Num Rate  Num Rate  Num Rate
 1851-1900   13 0.26    0 0.00   13 0.26
 1901-1950   29 0.58    8 0.16   37 0.74
 1951-1975   22 0.88    7 0.28   29 1.16
 1976-2000   24 0.96    7 0.27   31 1.24
 2001-2017   21 1.2    10 0.59   31 1.82

Data taken from Wikipedia lists of category 4 and category 5 Atlantic hurricanes:

https://en.wikipedia.org/wiki/List_of_Category_4_Atlantic_hu...

https://en.wikipedia.org/wiki/List_of_Category_5_Atlantic_hu...