The question however, what drive the prices to move from the lower to the central, and from the central to the upper as well as from the upper to the central and the from the central to the lower. This is driven by the carry trading activity of the carry traders. Carry traders however limit themself to buy the positive interest rate differential currencies pairs and to sell the negative interest rate differential currency pairs, thus the buy on the negative interest rate differential currency pairs and the sell on the positive interest rate differential currency pairs undertaken by the "momentum traders". Therefore, the BIS report that two common trading practiced by the large and largest market players are "carry trading" and "momentum trading". Momentum trading also called "trend following trading". More detailed information on the BIS market survey report.
Central banks however may not necessary to manage the lower and the upper ceilings due to the fact that both carry traders and momentum traders already antipate the ceilings, and it is called "honeymoon affect" by Paul Krugman.
Currently, the USD-band is underway to downward to the lower ceiling of the medium term exchange rate target zone ( NZDUSD , AUDUSD , CADUSD , GBPUSD , EURUSD , to downward), however after reaching their central bands/central parities, the carry traders carrying the NZD, AUD, CAD, GBP and EUR and to strengthen the NZD, AUD, CAD, GBP and EUR against USD, but their strengthening will not break their previous upper ceilings by the current major rebound driven by the carry trading activity. And, should the first tranch of the carry trading activity to be finished, those major pairs will resume to move to downward and to resume USD stronger than those currencies. How large the rebound driven by carry trading activity is the measure of their relative prices (weighted rates).
I long USDJPY , NZDJPY , AUDJPY , CADJPY (positive interest rate differentials) for their first upward tranch for 500 PIPs. In the future, I will re-sell NZDUSD , AUDUSD , CADUSD , GBPUSD , EURUSD (negative interest rate differentials) from their relative prices.Those long and sell to look for two source of profits, including interest rate differential rollover fees, AND by doing so, I can hold the trading positions to as long as required without any risk of swab fees or rollover charges.
The current rates for re-sell or sell on NZDUSD, AUDUSD, GBPUSD, EURUSD and for re-buy or buy the USDCAD are likely good for re-trading them to target their lower ceilings on NZDUSD, AUDUSD, GBPUSD, EURUSD and upper ceiling on USDCAD. Those lowers and upper ceiiings are presented in previous individual currency pairs analysis.