Reducing Outlook PST file size

[#1]

I am splitting PST files to group by date. I do this regularly at work to help manage file sizes.
I have copied the PST file and deleted a number of emails (Into the thousands) from each personal folder and yet the PST file size remains the same. I have looked for deleted folders and where found emptied and yet the PST file size remains the same. When I look in properties of the Personal folder, this suggests that the file size is greatly reduced. Yet PST file is still the same size.
Any ideas why the file size does not reduce

[#2]

The compaction process is a background task so the file size doesn't shrink immediately. 
https://support.office.com/en-nz/article/Reduce-the-size-of-Outlook-Data-Files-pst-and-ost-e4c6a4f1-...

[#3]

I vaguely remember going to Windows Control Panel, Email and using the "Compact Now" function in there for the PST file.
It will stay the same size on the hard drive until it has been compacted.

[#4]

Thanks folks. Had a 5% effect. And the deleted folders were already empty
Still can't understand  why the file size did not shrink after deleting the emails

[#5]

Deleting the emails just marks them as deleted.  They are still there, you just cannot see them any more.  You never see a reduction in the PST file size until you compact it and that can take hours for a large file.  Earlier versions of Outlook (up to 2002) stop working if the .pst file size exceeds 2 GB.

[#6]

Quote from: ReedRichards

Earlier versions of Outlook (up to 2002) stop working if the .pst file size exceeds 2 GB.

I think it was an inbuilt restriction on the file format so was also a problem with later Outlook versions if you used the older format, e.g. for compatibility/migration.
I run Outlook 2007 with multiple PST's and there's a mixture of types, and yes it was Outlook 2003 that introduced the new format.

[#7]

My .pst file (Outlook 2007) was 1GB but with careful deleting this evening and some archiving it is now 460MB.
I have a lot of emails with attachments I may look to archiving those as well.

[#8]

Outlook file size limit is 50 GB. My PST file  has been around since the late 90s and is just under 1 GB.

As with all systems good housekeeing is important...........................

[#9]

@Champnet 

The post prior to your post has been removed as spam and was on a subject from 2015.

[#10]

@Mav Poster wouldn't have been the first to reply to an old post, I assume they have something to add for future reference........

[#11]

@Champnet 

An Indian IP and other factors ensures I was correct in banning them and removing the post.