اين كلمه عبارتي تخصصي در علم اقتصاد به حساب مي رود و نه يك كلمه عمومي و
عبارت بالا به اين معنا است:

Developing countries have a large number of microenterprises and some large firms, but far fewer small and medium enterprises. In high-income countries, small and medium enterprises (SMEs) are responsible for over 50% of GDP and over 60% of employment, but in low-income countries they are less than half of that: 30% of employment and 17% of GDP.1 This SME gap is called the 'missing middle'.
و دقيقا نيز به كمبود بنگاه هاي اقتصادي متوسط اشاره دارد.
و يا باز تعريف مشابه ديگر:
The “Missing Middle” is a phrase that has been used relatively loosely in economic development discussions. But what does the term “Missing Middle” really mean? For some, the term has meant “a lack of SMEs in the developing world.”



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Note added at 9 hrs (2015-01-17 23:07:33 GMT)
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با ديدن پست قبلي شما كه درباره بنگاه هاي اقتصادي است از صحت معادل خود مطمئن تر شدم و فكر مي كنم با ربط اين پست به پست قبلي كه درباره بنگاه هاي اقتصادي است مي توانيد از صحت معادل من مطمئن شويد.