The unpredictable positive feedback effect of being first, achieving meteorically rapid scale makes picking winners hard.

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Here, the literature also points to a positive feedback effect with decisive expenditure-based fiscal consolidation because this type of consolidation appears to foster growth, in particular in times of severe fiscal imbalances.

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That is, there would be a positive feedback effect from health reforms and efficiencies - above all at the demand level by addressing ill health - and a negative one from failing to do so. (If anybody can calculate what 12.5% would be in today's money, then we know the difference between the Wanless "worst case" and what Mr Lansley warns about today).

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In this context, a network effect is a positive feedback loop whereby platforms with stronger ecosystem of developers, content and service providers attract more customers.

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Feedback received from individual participants and schools indicate that the RTLP is having a positive effect on learners and their families.

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