According to Sidney Harcave, author of The Russian Revolution of 1905 , four problems in Russian society contributed to the revolution. Newly emancipated peasants earned too little and were not allowed to sell or mortgage their allotted land. Ethnic minorities resented the government because of its "Russification", discrimination and repression, such as banning them from voting and serving in the Imperial Guard or Navy and limited attendance in schools. A nascent industrial working class resented the government for doing too little to protect them, banning strikes and labor unions. Finally, radical ideas fomented and spread after a relaxing of discipline in universities allowed a new consciousness to grow among students. Taken individually, these issues might not have affected the course of Russian history, but together they created the conditions for a potential revolution. "At the turn of the century, discontent with the Tsar's dictatorship was manifested not only through the growth of political parties dedicated to the overthrow of the monarchy but also through industrial strikes for better wages and working conditions, protests and riots among peasants, university demonstrations, and the assassination of government officials, often done by Socialist Revolutionaries." Because the Russian economy was tied to European finances, the contraction of Western money markets in 1899-1900 plunged Russian industry into a deep and prolonged crisis which outlasted the dip in European industrial production. This setback aggravated social unrest during the five years preceding the revolution of 1905. The government finally recognized these problems, albeit in a shortsighted and narrow-minded way. The minister of interior Plehve stated in 1903 that, after the agrarian problem, the most serious issues plaguing the country were those of the Jews, the schools, and the workers, in that order.. How many years did the prolonged crisis cause aggravated social unrest?