Causes of the European debt crisis historian Robert Skidelsky added that it was indeed excessive lending by banks, not deficit spending that created this crisis. Government's mounting debts are a response to the economic downturn as spending rises and tax revenues fall, not its cause. Either way, high debt levels alone may not explain the crisis. According to The Economist Intelligence Unit, the position of the euro area looked "no worse and in some respects, rather better than that of the US or the UK." The budget deficit for the euro area as a whole (see graph) is much lower and the euro area's government debt/GDP
Optimal foraging theory shown as a curve of energy gain per time spent in a patch (Figure 3). The curve starts off with a steep slope and gradually levels off as prey becomes harder to find. Another important cost to consider is the traveling time between different patches and the nesting site. An animal loses foraging time while it travels and expends energy through its locomotion. In this model, the currency being optimized is usually net energy gain per unit time. The constraints are the travel time and the shape of the curve of diminishing returns. Graphically, the currency (net energy gain per