This has been bothering me for a while now. Why are MSDS's apparently so inaccurate?

On many MSDS's I have read, rather than giving exact values they appear to give a range of a percentage that could possibly be insde the product.

For example these are the values for a commercial PVC pipe adhesive:

BISPHENOL A -EPICHLOROHYDRIN < 1%
Tetrahydrofuran 5-10%
Butanone 60-100%
Cyclohexane 1-5%
Ethanol < 1%

Is there a secret code here, or are these things just very vague?

"Trade secrets". It's vague (like DEA papers) for a reason.

Plus, if a substance does not reach a certain percentage it's not needed to be listen.

I'm with Shaolin here. It's possible that they don't have very accurate values for its composition (it may fluctuate from batch to batch), moreover, it's perfectly possible that it's not relevant for the product. Given that certain compounds are present below a certain concentration, they comply with the current laws and need no further description.

It depends what substance, what is its intended use, certification and where you get it from. If you are buying some hardware store fuel or whatever, they dont need to have so many guarantees (and therefore analysis to see if they comply with those guarantees) if you compare it with a USP grade chemical coming from a chem supply store. Certain chem suppliers can even analyse the specific batch before you buy, others are more general MSDS. I think depending what you are buying, its reasonable to try to contact the supplier and ask for more detailed information.

In any case I think in terms of safety, for the normal person just trusting MSDS is not enough, thats why we suggest in general that people check for their chemical in different ways (evap test for clean evapping solvents, read label, MSDS, email company if necessary/possible, reviews from others, etc)

endlessness: Pure chemicals aren't products therefore the details. Also some lab procedures require extremely pure chemicals.

Totally with you on the second paragraph.