The data transfer from PC to USB or from USB to PC depends on 3 main factors
1. Type and size of files being transferred
Music,video and office file will be transferred with a much higher rate compared to application files, you must have experienced this. If the files being transferred are relatively large, the speed of data transfer is higher.
2. Aging of pen drive
This point is common for any device, older pen drives have a very slower rate of transfer.
3. Port version of the USB
Nowadays almost every pen drive is a USB 3.0 device when such USB is inserted in a old system which has a USB port version of 2.0 the data transfer is drastically reduced.
Well the above 3 factors can not be controlled but there is a simple 3 step process which can give you the max out of your pen drive
ALWAYS SELECT NTFS FILE SYSTEM:
We cant transfer larger files(>4GB) if the pen drive dos not have NTFS file system. This can be done by formatting the drive with NTFS file system instead of FAT or FAT32.
CHECK FOR DISK ERRORS
Under the properties tab of pen-drive click on tools and then click on "check-now" button under error checking menu and start the scan to fix errors if any , depending on the size of pen-drive it may take some time
CHANGING DEVICE POLICY
Under pen-drive properties tab click on hardware select your USB device and click on properties. A new window should pop up. Click on change settings. Now move on to the policies tab and check better performance and at last click on OK.
Note: If you change the device policy and check on better performance then you must always eject your pen-drive only after clicking on safely remove your USB option in task bar and it is always recommended to remove the pen-drive from USB port when it is not in use.