The number of immigrants was equal to the number of emigrants at that time.

At that time the number of Maroccan immigrants was equal to the number of Turkish immigrants.

For the Turkish people between 1982 and 1985.

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Possible answers: unemployment is large within these groups, a stricter immigration policy, an improved perspective in the country of origin.

See the graph to the right.

Decreasing most 1980.

The two cyclists have covered the same distance at the points of intersection.

During the first $95$ minutes and between $115$ and $160$ minutes.

At around $40$ minutes, $95$ minutes and $140$ minutes.

$2600$ pieces; approximate profit $200$ kEuro.

After $1000$ pieces.

After more than $2$ months.

See table.

This point of intersection does not mean anything, because the number of horses and mules and the number of tractors have differently scaled axes.

That should be between 1950 and 1960. Only then does the number of animals fall under the $10$ mln. A small table clarifies this : in 1952 both seem to be around $4$ mln.