To do this I saved the spreadsheet as a CSV file, then used the textutils on it:
cut -d, -f16 spreadsheet.csv | sort | uniq -c
cut picks out a particular column. We need to tell it the file is comma-separated (-d,) and pick the 16th column (-f16). Then feed the results (|) into sort which sorts them alphabetically ready for duplicate removal. Pipe the sorted output into uniq which removes duplicates, with -c counting them as well. The result is a list of all values in the column, with a count of how many times each occurs.