Just ran through analysis on the data from NASDAQ symbol list. As of 13 Jan 2017, there are 12 different types of sectors.
|Sector Type||No. of companies||%||Market Cap (billion)||Market Cap %|
These include all companies listed on NYSE, NASDAQ and AMEX but excludes companies that are not categorized. as any of the above. As of today, there are 1550 companies that do not belong to any of the category above.
Market cap wise in %, it looks fairly similar to the number of companies which obviously makes sense. Looking at companies under Technology, with the rise of companies like Apple and Facebook, it probably explains why tech companies make up 12% of total but 17% of total market cap.