The purchasing power (value) of all locked in term currency investments is suspect and you generally lose by the end of the term. The cost of living increase, coupled with inflation and conversion fees almost always guarantees a loss over time.
In currency markets, to make money, one needs the ability to buy dollars when they are low and sell them on a day when they are higher, acquire euros when low and sell when higher, buy pesos when low and sell when higher etc, repeated as often as warranted. With today's economic realities and low interest rates, a term deposit although considered safe is usually a recipe for insignificant gains if not an actual loss despite the appearance of coming out a bit further ahead. That's how banks/investment firms make their money - they have floors of traders moving money around several times a day.
The only way to beat the banks is to let them profit and pass on to you compound interest over the long term which allows you to eventually realize increases over and above COL and inflation. This takes decades though.
The rich get richer by making lots of frequent large transactions. The middle class and the less well off have no such ability and are the ones preyed upon by the vultures.
Food is a good investment for the working class.
Eg. In 2013 a 5lb jar of peanut butter is $5.99. In 2015 that same jar of Skippy is $7.99. If one were to invest $5.99 in 2013, the interest earned up to 2015 would be insufficient to buy a jar of peanut butter. If, however, in 2013 one was to buy a lifetimes supply of peanut butter, one would not have to pay $7.99 in 2015 or higher in later years.
Coffee, rice and other staples never get cheaper, but they also don't have an indefinite shelf life so one can't plan on retiring with a warehouse full of peanut butter to be sold to fund other purchases. In the short term, one can come out much further ahead buy buying enough peanut butter (which usually has a shelf life of at least 18 months-two years) to avoid the intervening incremental increases in price than handing the same sum to a bank and hoping to come out further ahead.
Higher gains require a higher degree of risk and one needs to be able to lose it all to beat the curve. A well diversified portfolio of sufficient scale can result in a positive income but one needs to factor in that some of those investments will be losers and counter with a majority that will be winners. The average investor without significant resources to put into play only has compound interest in their corner and that what the market needs to fund all the other winners who are playing the short game while the majority accept the long game as their only real opportunity for actual gains.