Explain how portfolio size, cash flow needs, horizon, and regulatory and other limits constrain asset allocation

Size cuts both ways: large investors gain access to private assets, better terms and internal staff, but face capacity limits in small markets and market impact when trading; small investors may be unable to meet minimums or diversify across private funds. Liquidity needs, from spending, benefit payments or potential emergencies, limit the share in illiquid assets. Time horizon matters because an investor's risk capacity changes as human capital is consumed and liabilities approach. Regulatory and other constraints vary by investor: insurers face capital charges and asset–liability matching, pension plans funding rules, endowments spending policies, sovereign wealth funds political mandates, and individuals tax and legal restrictions. The trap is ignoring a binding constraint in favour of the unconstrained optimum.