Strasbourg, September 2: You may not have noticed it the last time you elbowed your way down the Via Veneto or tried to find a parking space in downtown Paris, but Europe is becoming emptier. That is what population study experts, known as demographers, from nearly 30 countries gathered for an eight-day conference were told yesterday. Although it may be an exaggeration to think of Europe as a ghost continent, experts said the ramifications of under-population should be taken seriously. The Director of the French Institute of Demographic Studies, Mr. Georges Bourgeois-Pichet, told his colleagues that some nations, namely West Germany, Denmark, Sweden and Portugal, were proving incapable of maintaining present population levels. He said the replacement of their future generations was uncertain. Mr. Bourgeois-Pichet offered statistics showing that the European birth rate had been declining since 1965. In the Soviet Union the drop began in 1958, and in Portugal and Holland it started in 1963, he said. Other population experts said that in the period from 1920 to 1960 the world population increased 60 per cent while that of Europe lagged with 31 per cent. Europe would account for an estimated 42 per cent of the population of developed nations by the year 2,000 whereas it now contained more than 53 per cent.