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US Market Data
- Overview
- Layout & Security Types
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- Historical Data
> Database Maintenance
- Custom Folders
- Update Schedule: March
- Update Schedule: April to September
- Update Schedule: October
- Update Schedule: November to February

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"Database Maintenance" is the process by which your US Stocks database is automatically kept "tidy" with respect to new listings, de-listings, symbol and name changes and price adjustments made to account for splits, reverse splits and other "capital events".

The following actions are performed as part of the daily database maintenance:

  • Historical equity prices are adjusted for changes to a company's capital base.
  • De-listed securities and associated trading instruments are moved from the main database to a "Delisted Securities" folder.
  • Securities that have undergone a name or code change are refreshed to reflect the new name or code.
  • New securities that have been added to the database are assigned their full names.
  • Securities that have changed their listing "location" (e.g. have moved from NYSE to Nasdaq or from Nasdaq to OTC) are automatically transferred to the appropriate folder with full trading history intact.

Can't I just use free data from the internet and do the maintenance myself?

It's theoretically possible, but a huge task in practice. Why spend all your time maintaining your database when you should be looking for trading opportunities? The table below shows the number of corporate actions that Premium Data processes in a typical year:

  Average Maintenance Actions Per Year
Exchange Capital Adjustments (e.g. splits & reverse splits) Company Name Changes Symbol / Company Name Changes Symbol / Company Name
& Exchange Changes
AMEX 18 114 30 30 84
Nasdaq 342 168 600 432 342
NYSE 210 492 66 96 96
OTC 360 450 6228 60 456
TOTAL 930 1224 6924 618 978