Dramatic change in intrinsic value within a short space of time

I had made a list of stocks and their intrinsic values to help create a portfolio. I hadn't got around to making one and found that a lot of the stocks' intrinsic values had gone down dramatically, although their prices had not changed much. This has happened with defensive stocks as well.
Taylor Wimpey (enterprising) is an example - 100.5% IV when I bought it around a week ago and now it's at 1.07%. It is cheaper now than it was then..
Bellway (defensive) was another hat looked very tempting until I read it had gone down to 1.8% IV from well above 100%. It is also cheaper now.
Could this be a result of the uncertainty or irrationality of the market, and we shouldn't pay the sudden drop much attention?

Stocks Discussed: 
Bellway PLC (BWY.L)

Dear Jeff,

Thank you for your forum post!

While the Intrinsic Value(%) of a stock can change every day with the price, Intrinsic Value only changes when a stock's fundamental data gets updated (formula given below). Such drastic changes need not always be taken too seriously, as a simple 1% drop in one of the Graham criteria can sometimes result in a completely different Graham Grade allocation.

But unless the stock in question is an NCAV grade one which requires an EPS (TTM), such changes should only happen once a year. Neither Bellway PLC nor Taylor Wimpey have recent Fiscal Year values.

Is it possible that you're looking at different listings of the same stock on different exchanges?

Both the above stocks are listed in four different exchanges and have different Intrinsic Values in each. For example, Taylor Wimpey PLC (TW.L) has an Intrinsic Value(%) of 1.07% and Taylor Wimpey PLC (TWW.BE) has an Intrinsic Value(%) of 92.13%.

Such differences are quite common because of different dividend payout histories in different regions and so on.

Intrinsic Value(%) = Intrinsic Value ÷ Previous Close

I don't think they were on different exchanges, I made sure that each UK stock had a .L at the end of it. Perhaps I looked at it before and after the annual data had been changed.
The TW.L has the previous close at 142.55 at the moment, and the shares are actually pence, not pounds, which I think should correct my problem if the intrinsic value is in pounds.

It has been suggested that some companies 'cook their books' to make them look more prosperous than they are. What sort of things might a company do to appear better on Serenity Stocks? China Yuchai International LTD (CYD) is supposed to have an IV of around 1,300%, which looks very high, although I have not looked into the company much further.
I can't work out how to analyze stock myself through Serenity. Is there another analytical website you recommend? I have also found it difficult to find all the information required for Serenity using one website.

Dear Jeff,

Thank you for your comment!

It appears Serenity's data vendor started listing U.K. stock prices in GBX (pence as you rightly observed), while the fundamental data continued to remain in GBP. This was causing most U.K. stocks to erroneously fail Graham's criteria. The issue is being clarified with them.

But in the meantime, all U.K. stock prices on Serenity have been adjusted to GBP from GBX. So you should now see a lot more stocks clearing Graham's framework on Serenity's screeners.

Regarding the issue of cooking the books, Graham's framework is designed to compensate for all typical accounting adjustments that fall within regulations. However, if a company falls outside one's legal jurisdiction and has the option of fearlessly fudging numbers, there's really not much any analytical framework can do.

This issue is a cause for concern across global investment regions and has not yet been addressed satisfactorily in any of them. For now, it would seem prudent to invest in companies that are domiciled within regulatory jurisdictions that one is comfortable with.

Lastly, a full Graham analysis requires several dozen financial figures for each stock and Serenity's raison d'être is that there exists no other single service that provides all the required data or a similar analysis. Serenity's tutorial link and video include a sample analysis that should help clarify how the full Graham framework is applied.

Graham Resources