How much better is HF reception outside of cities?

It's long been a dream of mine to have a location for HF reception in a quiet place outside of the city. Since we moved to Thornbury about two years ago I've been plagued with high levels of broadband noise which has left the HF spectrum, particularly on 40m, at often S9 +20 DB. 

That's the worst example. Amazingly even through high-level noise like this digital modes such as WSPR can still receive a few signals and I'm able to copy Steven VK2BLQ sometimes.

The dream of a second location has finally come true with the purchase of 5 acres north of Melbourne at a place called Drummond. 

40m looks completely different here:

Between signals it's S0 most of the time.

To measure the difference in signal-to-noise, Stephen transmitted five watts of WSPR from Sydney and I received simultaneously in both locations. The difference is huge. The largest difference I saw was 21dB better signal-to-noise at the country location!

Here is WSPR reception of stations more than 400km away:

For the initial setup, the antenna is far from optimum, it's just a wire dipole hanging up right next to the house with some coax going in through the kitchen window. This can be greatly improved in the future.

How much better is HF reception outside of the city I measured at up to 21dB.

PS: Unfortunately it's going to take me a while to improve antennas as during the initial move in I missed a step and fell heavily, breaking my left arm. This post has been written using the Apple built-in dictation system which I find to be excellent.