Final answer:
The true statement based on recent studies by PwC and PMI is that higher project management maturity leads to higher performance in organizations. It has also been generally acknowledged that project management training significantly contributes to business success.
Step-by-step explanation:
The question you asked pertains to the correlation between project management maturity and organizational performance based on studies by PricewaterhouseCoopers (PwC) and the Project Management Institute (PMI). Among the statements provided, the one that recent studies support is that higher project management maturity yields higher performance. Studies like those conducted by PwC and PMI consistently find that organizations with more mature project management practices experience better project success rates, efficiency in delivery, and adherence to budgets and timelines.
Regarding the other statements, the evidence tends to contradict the notion that project management maturity is declining on average; it is generally acknowledged that there's been a global push for better practices in the field. Also, empirical data on specific percentage increases in project success rates since 2008 may vary, and without a specific study to reference, it's challenging to confirm such a precise figure. Lastly, it is generally accepted in the professional community that project management training is valuable and contributes significantly to the overall performance and success of businesses.