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Hi all,

Been a long time lurker but appreciative of the humour and wisdom at HPC :)

I hope you don't mind but could think of no better place to first mention a website I've been working on for too long - http://www.housepriceobsession.co.uk

I would be grateful to hear any feedback. It has been a labour of love and is still a work-in-progress to a degree with a few pieces I'm still working on, and some new exciting features that I hope to release over coming months, but do please reply with comments, changes, suggestions and ideas.

I, probably like many on the board, found the simplicity and usefulness of Dan's original houseprices.co.uk site very addictive, so that was part of the original inspiration plus I wanted to add calculations for properties which have multiple sales which I found myself doing manually when comparing properties. I actually only came across evictee's site towards the end of my project, and houseprices.io is undoubtedly extremely quick, but I must acknowledge his efforts there, and not just the speed of the site.

Please do share the site with friends and colleagues - am hoping the site is useful for others apart from me

Thanks!

 

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Bug report:

1: When sale price and sale data is known, it doesn't always fill in the change columns.

2: Estimates are really high, even higher than Zoopla. 

3.Select columns - seems odd that the address is listed, blanked out then not selectable

4. If there are two sale dates, why give two estimates?

5. When going full-screen on the streetview picture, I get the wrong aspect ratio (thin picture in middle, large black above/below)

 

Embedding the StreetView and the map works really well.

Allow ordering by address rather than sale date?

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9 minutes ago, VeryMeanReversion said:

Allow ordering by address rather than sale date?

Click on the word "Address" in the address column. However, it would be great if it could evaluate house numbers (rather than just doing a literal string compare) so that house number 2 through to 9 appear before number 10.

Agree that the current valuations are too high.

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31 minutes ago, VeryMeanReversion said:

Bug report:

1: When sale price and sale data is known, it doesn't always fill in the change columns.

2: Estimates are really high, even higher than Zoopla. 

3.Select columns - seems odd that the address is listed, blanked out then not selectable

4. If there are two sale dates, why give two estimates?

5. When going full-screen on the streetview picture, I get the wrong aspect ratio (thin picture in middle, large black above/below)

 

Embedding the StreetView and the map works really well.

Allow ordering by address rather than sale date?

Thanks for the feedback VRM, much appreciated.

1. Noted. Will try to make it clearer as to why the change data is missing. For the first (earliest) transaction for a property, there is no change, hence no calcs can be made.
2. Noted and will look into the estimating.
3. Valid point again - will probably remove address from the selector (the address column probably needs to always be shown)
4. Good question. The thinking was that it could be interesting in some cases to see what the effective estimate is based on each paid price. One buyer may have underpaid, another may have overpaid etc. As local area experts, we often have a good idea as to what a fair price is at a given time for a property, so may help to know the various estimates.
5. Was on my list, and had already had a look but will try to fix asap!

Re column ordering, most of the other columns should allow reordering by clicking the column heading... can you let me know if that's not the case pls?

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28 minutes ago, Broken biscuit said:

Click on the word "Address" in the address column. However, it would be great if it could evaluate house numbers (rather than just doing a literal string compare) so that house number 2 through to 9 appear before number 10.

Agree that the current valuations are too high.

Thanks BB.
Good spot and reminder on address ordering. Will try to pick this up asap.

Valuations - can you pm me one or two postcodes and specific paid prices I can investigate pls.

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I like it! B)

Hope to see the site succeed and evolve further.
I'd like to see historic pricing carry the currency inflation adjusted values (mouse over perhaps) or check box option maybe. Would impact % columns but delivery more accurate meaningful information, especially noticable for price data more than 5 years old.

 

 

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30 minutes ago, Andy T said:

Could it do partial postcodes/ postcode areas?  i.e 'M21' instead of a full postcode or area name?

Yes it does.  I found this feature really useful. 

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30 minutes ago, Andy T said:

Could it do partial postcodes/ postcode areas?  i.e 'M21' instead of a full postcode or area name?

Partial postcode searches should work but as you have discovered, trips up for postcodes beginning with a single letter (B, E, G, L, M, N, S, W) - this is now on my list :/

Thanks for flagging Andy

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1 hour ago, DarkHorseWaits-NoMore said:

I like it! B)

Hope to see the site succeed and evolve further.
I'd like to see historic pricing carry the currency inflation adjusted values (mouse over perhaps) or check box option maybe. Would impact % columns but delivery more accurate meaningful information, especially noticable for price data more than 5 years old.

 

 

Glad you like it DHW and thanks for the encouragement there. Early days but have got ideas for the site to be developed further and in different ways.

Will look to incorporate the inflation adjustment feedback into the calculation columns, good feedback B)

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The estimates are off the top of the scale but seem to reduce with the sales over the years, is that a bug and they are displaying in the wrong order? The 1999 estimate is miles higher than a 2016 estimate and both higher than the 2016 sold price.

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15 hours ago, sPinwheel said:

How is the estimate calculated?

I was about to ask the same, as having looked at the estimates of properties for sale...the estimate appears to be anywhere between 10-20% more than the current asking price.

Useful website though, thanks !

Edited by ItalianV6
.

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1 hour ago, ItalianV6 said:

I was about to ask the same, as having looked at the estimates of properties for sale...the estimate appears to be anywhere between 10-20% more than the current asking price.

Useful website though, thanks !

I too would be interested to know how the estimated price is arrived at. They seem too high compared to any of the main indices that offer regional data. The estimates are even higher than Zoopla -  the most bullish of all the estimators.

I suspect a simple mathematical error somewhere.

Edited by Broken biscuit

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Thanks for all the feedback so far, a handful of fixes were applied early this morning:

Changes:
- removed full screen on the streetview panorama as a temporary fix - thanks for the nudge VeryMeanReversion
- added support for full and partial postcode search for outer postcode prefixed with B, E, G, L, M, N, S, W - thanks AndyT
- fix for address sorting (icon was incorrect on first sort, and issue toggling between asc/desc)
- improved address sorting which handles string and numeric and mixed primary and secondary address elements - thanks Broken biscuit, VeryMeanReversion 
- removed address checkbox from column selection - flagged by VeryMeanReversion
- fixed order of sales within each property group when multiple transactions exist and sorting on address, this issue is outstanding if sorting on property type. Thanks for flagging Democorruptcy

 

High estimates:
With regard the estimates being high, even higher than zoopla, and even more alarming, higher than current asking prices - there are a couple of points to this:
- firstly, the biggest variable going into the estimate is the price paid. If someone overpays for a property, the estimate is almost certainly to be on the high side. If someone underpays for a property, the estimate is likely to be on the low side. You can see this with Zoopla's estimates and the same with those on housepriceobsession.
- for specific cases of overly high estimates, can you give me specific addresses (postcode + primary and secondary name elements) and I can investigate and clarify.

 

The Colonel's Secret Recipe:
As to how the current price estimates are calculated... I was positively surprised that people were interested and am happy to open this up rather than it being a secret.
        current price estimate = previous sold price * % change in Land Registry Index between sold date and current index value

The current index value is derived using a long moving average because the Land Registry only publishes up to ~2 months in the past.

The calculation tries to use the Land Registry index series matching against the local authority for the sold address - this is the most granular and relevant. If local authority index series can be matched, a county-level series is used.

I will look at making a further change today/tomorrow to pick up the exact index for the property type (detached, semi, terraced, flat etc.) to fine-tune the accuracy. Interestingly, and at first glance for one series, flats seem to appreciate more than houses, followed by terraced, semis, then detached. That's another topic though.

The more I investigate Zoopla's estimate compared to housepriceobsession.co.uk, the more I am inclined to think they do something very similar to the above, and may even use LR index values. They possibly use a different index series source, they possibly use a different moving average, or match against a series for a different location/region. Happy to concede if any of these assumptions are wrong though.

Will add this explanation to the FAQ!

Am open to feedback on the estimating calculation :)

Thanks!



 

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Hi Badger,

Thanks for being open and publishing the "Colonel's secret recipe". I've just checked a few properties around my way using your method and I have to admit - your maths does indeed appear to be correct (which is depressing for anyone looking to buy:()

The Land Registry appears to have reported higher HPI than I had previously realised, particularly when taking into account the type of property.

Well done for creating the site and good luck earning some income from it.

Edited by Broken biscuit

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1 hour ago, badger2 said:

The Colonel's Secret Recipe:

As to how the current price estimates are calculated... I was positively surprised that people were interested and am happy to open this up rather than it being a secret.
        current price estimate = previous sold price * % change in Land Registry Index between sold date and current index value

The current index value is derived using a long moving average because the Land Registry only publishes up to ~2 months in the past.

The calculation tries to use the Land Registry index series matching against the local authority for the sold address - this is the most granular and relevant. If local authority index series can be matched, a county-level series is used...
 

Do you mean extrapolating to now using a moving average? Bear in mind "A 3 month moving average has [already] been applied to estimates below the regional level".
https://www.gov.uk/government/publications/about-the-uk-house-price-index/about-the-uk-house-price-index#calculating-the-uk-hpi

 

 

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2 hours ago, badger2 said:

Am open to feedback on the estimating calculation :)

While I'm not enough of a statistician to comment on the calculation algorithm, I do think the figures come out a bit high. A house that sold for £230k in 2007 is estimated to be around £339k. It was actually sold as a repo from a bankrupt BTL landlord in 2011 for £183k but that does not appear in the land registry published figures because it might disrupt the market dont-cha-know.

Next door changed hands in 2014 for £230k and is almost an identical build but has no conservatory. I'd reckon on £250 to £290 if it went on the market today. Another house in the same village changed hands at various prices and appears to have gone from a terrace to detached. Its actually an end of terrace that was sold to builders who built two houses on the garden. This accounts for the price fluctuation but not for the change in status.

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