When the roof becomes unreachable.

Picture the villages of Kent and Essex in spring 1381. The Black Death killed nearly a third of the population thirty years earlier. Land has become scarce. Lords are raising rents and labor duties brutally.

An average peasant must now give half or more of his harvest simply to stay on the land he has farmed for generations. You can smell the wet earth, hear the plows grinding to a halt.

Families crowd into tiny, cold, smoke-filled cottages. Children are hungry. Parents watch the lords' great estates expand while they are evicted or crushed by debt.

A simple poll-tax has just been doubled. It's the last straw.

In a few weeks, thousands of peasants rise up. They march on London, armed with scythes and clubs. They burn tax registers, open prisons, execute tax collectors. The young King Richard II must meet them in person at Smithfield.

Paris, 1788. An artisan climbs the narrow, dark stairs of his building. Rent has tripled in twenty years. So has bread.

Wealthy aristocrats and financiers buy entire buildings to rent at premium prices. Families crowd into tiny, damp, unsanitary rooms. You smell mold and soot. You hear the arguments in the courtyard, the children crying because they are hungry.

The common people watch the nobles' grand mansions expand while they are pushed out. The insane housing ratio becomes a slow poison. Elites grow rich on land rent while the people are driven out.

The dam breaks in 1789. The homeless and enraged tenants take to the streets. The Bastille falls. The French Revolution explodes.

Winter 1916. Picture the frozen villages of the Tsarist Empire. Peasants, bent over, return home after a day's work on fields that no longer really belong to them. The great estates of nobles and the Church stretch as far as the eye can see.

An average peasant must give half or more of his meager harvest simply to stay on the land he has farmed for generations. Meanwhile in Saint Petersburg and Moscow, factory workers live in squalid barracks, paying exorbitant rents for rooms shared by ten.

The tsar and the great landlords grow rich. The small peasants and workers are locked out of land and housing. Anger builds silently for years.

Then, in February 1917, the dam breaks. The women of Petrograd take to the streets demanding bread. In a few days, the revolution explodes. The tsar abdicates. In October, the Bolsheviks take power with their simple powerful slogan: "Peace, bread, land!"