Based upon my experience (not my research), I have found that most organizations do not do a good job with regard to their strategic planning and also in some instances have found organizations developed unrealistic goals and expectations. 

This is one billion dollar question. 

All the goals are set based on expectations. The main problem is the incorrect expectations for the internal performance and the behavior of environment . 

A firm can reduce the failure by conducting many approaches to enhance its expectation and to come over its weakness in order to achieve its goals that are based on a high confident expectation.

Though looks simple, it is a complex question which challenges all the organizations ! The percentage may vary depending on the study group, the sample size and the sample populations, as some other study have shown little more percentage. The answer to your question depends on a lot of factors. The most important ones are: business processes are not integarted with the strategic goals, or if they meet on papers (by the management) it is not cascaded down the hierarchical ladder of the organization; or due to dynamic situations like frequent changeover of CEOs/key personnel; technological cganges (IT, Condition monitoring tools like sensor technology), knowledge management issues (like older generation with experience are retiring and their knowledge is gone without retaining in the organization, less training); and non-integration of the personnel with the management information (transprency of information, i.e. every personnel talking same language within an organization) etc. There are number of publications and case studies on this topic. You may like to go though them to get more detailed answers.

Adding to Parida's answer, a number of functions find there is considerable strategic ambiguity when referring to  documented strategic plans. They look at documented plans, but do not understand how or where their unit fits into the picture. It is also important to note that unrealized strategies from formal planning is a normal thing, and not t be unexpected at all. It also does not directly translate to poor organizational performance. Strategies emerge as much as they are planned. Actual strategies may emerge as a a planned strategies struggles for any number of reasons. Accordingly, new ones emerge in their place. These can be highly successful. So while 13% of planned strategies are said to be realized, the performance of these organizations would unlikely be a reflection of this figure. If you are interested more in this domain I would  recommend reading Regner's article that compares a case of planned strategy and a case of emergent strategy. Very interesting. Regner, P. (2005). Adaptive and creative strategy logics in strategy processes. Advances in Strategic Management, 22(5), 189-211. 

Further to my previous, I can suggest all researchers and industrial professionals to follow ISO 55000, 55001 and 55002, which integartes the business processes with asset management and strategy throughout the organization.

Setting and achieving strategic goals by an organisation essentially has two components in it, namely, (a) Planning the Goal and (b) Execution of the Plan towards Materialisation of the Goal. 

In general there are many processes and involvement of various groups of people in the planning as well as in the implementation stages. There can be lack of coordination at many points leading to failure in meeting the target.

In addition to the aforesaid reason, there is a general tendency to plan an unrealistic goal, which may at the end give rise to failure in achieving the same. 

IMO there are three main reasons and they have been touched upon here that can cause planned stategies to not play out. (1) Poor leadership vision; (2) Expectations are not shared by the whole (intent has to be incorporated within every part of the organization...this is a discussion and agreement between all parties as a shared covenant); and (3) Tools (shared networks....work environment is open; process capabilities are known within and between process owners; collaboration encouraged and facilitated by all members, etc.).  We need to put in place the ability to flex the organization when it needs to change processes within the corporation's network (a network approach to tie the processes of the organization under the intent...read Enterprise Architecture).  All three of these can be expanded with more discussion and with ancillary tweets.  From my personal experience in both manufacturing and marketing, is the link between these major parts of an organization has to be aligned as flexing for the customer needs can only be met by changes in the products or production as this environment is very fluid especially in the global economy today.

This is an intuitive response and not based on researching this question. Possible explanations include any and all of the following:

1. Unrealistic or poorly defined Corporate strategic goals.

2. Unrealistic Functional Area strategic goals.

3. Individual functions strategizing unilaterally, and without "systems thinking,"  (i.e., strategize for the benefit of all as opposed to just the self).

4. Mismatches between Corporate and (some or all) Functional Area strategic goals such that they work at cross purposes.

6. Lack of sufficient "buy in" from some or all of the parties involved. This involves buy in from management and buy in from non-managerial employees.

7. Lack of leadership -- top management must make sure everything is driven by corporate strategy and the latter is not just window dressing or a document that gathers dust once it's prepared.

8. Inability to effectively translate (Corporate and/or Functional) strategies into clear action plans. Action plans are either non-existent or do not dovetail well with strategies.

9. Inability to effectively translate action plans into actions.

I believe that about covers likely explanatory factors off the top of my head. As can be seen, there are multiple points of possible failure between articulating a strategic vision and executing it. The larger and more complex an organization is, the greater the risks in each of these regards. I do not know to what segment or segments of the corporate world the 13% figure applies and to what extent was strategy not realized in individual cases. But I would look at factors related to the above list in trying to find out why in each case.

I would like to add to what others contributed to this interesting question. In my view, strategy itself is based on hypothesis. Consequence may lead to type-I or II errors.

Interesting question. As I read why company fails to accomplish the goal of strategy. It is a complex question to answer, matter is whatever strategy is done at present need to be accomplished in future. Future is not in control but we can maximise. Yes, but the we should now the "theory of everything- and theory of nothing". Strategies can be controlled by scientific application of theory of everything, because everything connected to everything, strategic aspects are all about everything. 

I would like to work on this issue in collaboration  with an intending researcher(s) with inter disciplinary interest. 

The formalization of the strategy requires an assessment of the internal conditions in operational terms according the assumptions of goals to achieve. Without the appropriate assessment of existing organizational capabilities, the goals probability will not be achieved, which is also related with the adjustment of the organizational capabilities to achieve the strategic goal. This adjustment requires changing the organization current work (processes) to an intended state (to-be) supporting the business goals.

The internal adjustments should be developed in structurally and simultaneously with the articulation of the work (processes).

The lack of a proper strategy operationalization could lead low percentage of organizations achieving their business objectives.

This is a very good question. Thanks for posing it Mathias Kirchmer.

As Pedro Sobreiro pointed out above, having a plan on internal conditions is a prerequisite, but curiously having such a plan is no guarantee for accomplishing the goal, i.e. meeting strategic objectives. As a German field marshal, von Moltke, once observed; no plan survives its first encounter with the enemy. Likewise here. The plan must be amenable to changing circumstances. I think it was Churchill who shared a view on that; to improve is to change, to be perfect is change often.Of course the following question is whether one knows in which direction to change next?

I think that the existence of such uncertainty drives the low performance on reaching objectives. Can it be managed? To some extent I think that is the case. Can it be completely controlled? That I sincerely doubt.

I agree with Pieter Griend having a plan doesn't mean that are accomplished the underlying assumptions of the business goals. This should accomplished in a context of the organization existing business capabilities with the plans reflecting what the organization must change in its business capabilities to achieve the intended goals. This should be supported with adaptability in a perspective of adjustment of the organization with the external environment (e.g. as describe by Teece in Dynamic Capabilities and Strategic Management) and supported in Business Process Management used to adjust the work according the goals to be achieved.

The organizational adjustment should be supported in its Business Capabilities as logical construct to support the development of operational plans implementing the strategy. As Dwight D. Eisenhower describes "Plans are nothing; planning is everything. "

Thanks for all the interesting feedback. I think establishing a BPM-Discipline which focuses on moving strategy to execution is key. This enables the operationalization of a business strategy and with that the cross-functional execution of appropriate people and technology initiatives.

I think that the creation of a discipline with the underlying concern how to operationalize the strategy very interesting. Another aspect that could also be relevant is how this discipline could contribute to the development and articulation of other management disciplines, like human resources, marketing or strategy.

It is a well known fact that most of the organizations and its operation is hardly able to achieve its strategfic objectives. Under todays' dynamic global business scenarios with complex assets of all types, viz; engineering, hunan, information and knowledge etc, to find a holistic and balanced perfosmance is a big challenge. No single or mixed technique or models are going to find a total solutions. Ealier, industry tried to follow the balanced scorecard coupled with ISO 9000, yet it could not find the soölution. Now we have ISO 55000 which looks into all contexts of asset management (all types of organizational assets: physical, human, tangible and intangible). If it is interpreted in the right perspective for the organization to meets its unique requirements of the strategy, perhaps a balanced and holistic solutions could be found and the this 13% may indrease to many fold !!