Trend 3:
More prepositions, fewer datives:
Whereas in the past the German verb “haften” – which means to be liable – had to be followed by the dative case, nowadays collocations of the type “haften gegenüber” – literally speaking to be liable to, towards or vis-à-vis somebody – are used more frequently: “Der Verkäufer haftet gegenüber den Käufer”. Here, a preposition is used in modern German where previously the dative case was sufficient, as in “Der Verkäufer haftet dem Käufer”. The same holds true for “kaufen” and “verkaufen”; at least, this is my impression. Formerly, you would read, “Der Verkäufer verkauft dem Verkäufer xy”, whereas today you will find more frequently, “Der Verkäufer verkauft xy and den Verkäufer.
Or take “abtreten”, which means to sign or to transfer. “Zusätzlich tritt die Verkäuferin ihre IP-Rechte an die Käuferin ab” was not very common 20 years ago, whereas you increasingly see it in modern legal texts. The old gold standard was “Zusätzlich tritt die Verkäufer der Käuferin ihre IP-Rechte ab”, i.e. using the dative case.