Here is another approach using [`EntityValue`](http://reference.wolfram.com/language/ref/EntityValue). The countries:

	countries = Map[
		Entity["Country",#]&,
		{"France","Germany","Spain","Russia","Portugal","Poland"}
	];

Using [`EntityValue`](http://reference.wolfram.com/language/ref/EntityValue):

	interval = Interval[{DateObject[{1999}], DateObject[{2008}]}];

	dataset = EntityValue[
		countries,
		{
		EntityProperty["Country","GDP",{"Date"->interval}],
		EntityProperty["Country","Population",{"Date"->interval}]
		},
		"Dataset"
	];

The dataset contains the information you want, although the values are encoded in [`TimeSeries`](http://reference.wolfram.com/language/ref/TimeSeries)/[`TemporalData`](http://reference.wolfram.com/language/ref/TemporalData) objects. For instance:

	ts = dataset[[1,1]];
	Head @ ts

>TemporalData

To extract values from a [`TimeSeries`](http://reference.wolfram.com/language/ref/TimeSeries)/[`TemporalData`](http://reference.wolfram.com/language/ref/TemporalData) object you give it the date you are interested in:

	ts[DateObject[{2004}]]

>Quantity[2.12411*10^12, ("USDollars")/("Years"), {}]

So, to obtain the population of Russia in 2004:

	dataset[Entity["Country", "Russia"], 2, #[DateObject[{2004}]]&]

>Quantity[144306982, "People", {}]

Or, the average GDP for all of the countries for the year 2002:

	dataset[Mean, 1, #[DateObject[{2002}]]&]

>Quantity[8.27107*10^11, ("USDollars")/("Years")]