Firstly, some barrage of stats :
- Average growth (GSDP) between 1994-02 was 3.6%
- Average growth (GSDP) between 2001-12 was 6.3%
- Per capita income in 2000-01 was Rs. 9,980/-
- Per capita income in 2011-12 was Rs.21,734/-
For further comparisons related to bifurcation of Bihar see Did Jharkhand progress after getting separated from Bihar?
In terms of pure economics: laissez Faire theory (trickle down effect ) began to work wonders once bifurcation was achieved. Again, I risk being labelled too much of an ‘optimist’; in the same decade Uttarakhand’s per capita Income grew from a comparable Rs.14,ooo/- (approx.) to well over Rs. 44,000/-(approx.) .
So, what was ‘that’ which drove Uttarakhand’s relative prosperity?
In one word: stability.
Since, bifurcation of U.P. & creation of Uttarakhand; by carving out the hilly districts, three state elections were held : 2002,2007 & 2012. The first two legislative assemblies completed their terms whereas, the third stands incumbent.
Contrast the same with the state of Jharkhand:
There were a total of 10 governments, President’s rule was enforced 3 times & it doesn’t help that an independent candidate went on to become the state’s head (Madhu Koda).
It’s quite evident that Jharkhand is a political quagmire with instability at the helm of power impeding it’s growth. There are obviously other factors: the menace of Naxalism & Adivasi issues which demand earnest efforts from the government. They can no more put up some whimsical remedies each time the state is bound for polls.
Fortunately, the present government led by Raghubar Das has enough leverage to see off any political challenge & may very well set the trend for decisive mandate in future elections.
As an add on:
Weaker governments at the top of large mineral reserves ( as in case of Jharkhand) are prone to arm-twisting by large conglomerates. It serves them well to extract exorbitant returns from a government sitting on quick-sand using the clout of lobbying. On the contrary, stable governments can put a check to Machiavellian interests of industrial houses.
 & : Planning Commission
(This post appeared as an answer on Quora)