Among the given options, the one that is not a reason for excess demand is: Fall in propensity to consume

A fall in propensity to consume (the proportion of income people spend on goods and services) actually works in the opposite direction of excess demand. It reduces consumption, leading to less demand for goods and services. Consequently, it wouldn't contribute to a situation where demand exceeds supply. Excess demand is generally associated with situations where aggregate demand surpasses the aggregate supply in the economy. The options—reduction in taxes, increase in investments, and increase in government spending—are factors that can contribute to an increase in overall demand, potentially leading to excess demand.

• Reduction in Taxes: Lower taxes increase disposable income, leading to increased spending and potentially creating excess demand.
• Increase in investment: Higher investments boost economic activity and income, potentially fueling further demand for goods and services.
• Increase in government spending: Government spending injects money into the economy, increasing aggregate demand and potentially pushing it beyond the available supply, leading to excess demand.