If equity markets decline in value, you will know whether or not this affects your retirement income. Before taking the first retirement income check, the WPS states in a clear, bold font how a large decline in the portfolio may lead to a small decline in income. Usually, the WPS factors are something like a 20% decline in portfolio value leads to a 10% decline in income. A retiree who knows this in advance can plan accordingly, and feel secure that she will be safe later in life.