Lying as part of the Czech national culture started with the communist takeover right after WWII and established its roots so deeply that it reached a state of confabulation. Confabulation is "the confusion of imagination with memory, and/or the confusion of true memories with false memories." Basically it is when you start believing your own lies. The Czech Republic is in a state of confabulation.
A few examples to ponder: the decrees of President Benes in 1945, which caused irreparable harm to millions were lies - and millions knew they were lies, but the Czechs believed it then and believe it now. They even honored those lies recently by passing the new "Lex Benes" law. Then there were the political trials in Czechoslovakia in the early fifties everyone knew they were lies, but they believed it then and they believe it now. Can you imagine that the Czech Republic adheres to "legal continuity" with laws from the early fifties? Laws of the brutal terror of communism?
They lied (and knew about it) about the non-existent successes of socialism in the sixties, they lied about the Prague Spring in 1968 and their own confabulation made them believe that "reformed" communists like Dubcek, who tyrannized them a few months earlier, were now to make their lives better. Is it possible that 15 million people simultaneously suffer from Korsakoff's syndrome and (to quote Wikipedia) "confabulate by guessing an answer or imagining an event and then mistaking their guess or imagination as an actual memory?" It happened!
Russian tanks ended that psyched-out happening with the Prague Spring, but mass lying, confabulating and brainwashing continued. They lied on (and believed it) about their love for the Soviet Union and their inhumane system; they lied (and believed it) about "normalization" in the seventies and eighties.
Everybody with half a brain knew that the Velvet Revolution was just a KGB/StB prepared "changing of the guards" but nobody thought about stopping the lies. So they continued. Vaclav Havel, the darling of western liberals, made the whole Velvet revolution a lie by ensuring that not a single communist murderer or tyrant was punished. Nobody said a word. Vaclav Klaus, Havel’s successor, is lying about his imaginary successes in the West as an "economic lecturer" and ten millions of Czechs eat it up.
Senior officers of the Czech Army who just a few years ago were hard-line communist officers of the Czechoslovak Army (a Warsaw Pact member) now reside in NATO offices in Brussels - which rendered NATO effectively useless. Very large portions of Czech Republic representatives in EU posts are ex-communists. It is no secret that Czech representatives at the European Court of Human Rights in Strasbourg busy themselves by lying about the number of complaints coming from the Czech Republic and hiding them from non-Czech speaking judges. A cartoon I saw recently, deriding the European Union as a "new socialist super state," was probably depicting things the way ex-commies from Eastern Europe would love to have them.
So, do we have historical data to prove a pattern of pathological lying at a national level or not?