However, after the prosperity of 1924-1925, an economic crisis erupted that proved to be the worst to hit the pre-State Jewish Yishuv ("the Fourth Aliyah crisis"). Businesses began to collapse, there was a slump in the building industry, which had been the leading branch of the economy, unemployment reached a peak and thousands of Jews left the country. The Zionist enterprise was in danger. Weizmann searched unremittingly for financial aid to strengthen the Yishuv and in 1927 recruited influential non-Zionist American Jews to take action in Eretz Israel. In 1928, the Joint Palestine Survey Commission completed its work, which paved the way for the establishment of the Jewish Agency in 1929 (to be discussed in the next chapter).