Because per capita income is generally increasing over time all across the United States, we also need a benchmark against which to measure and compare the governors' economic performance. My benchmark is per capita income across the whole U.S.
I collected information from the U.S. Bureau of Economic Analysis and calculated the ratio of per capita income in each state to per capita income in the whole U.S. Then I examined the ratios of each state run by the 10 candidates who are current or former governors in the year they took office and the year they left office (or in 2014 for those still in office). By subtracting the earlier ratio from the later ratio, we can determine whether the state's economic performance improved or worsened during the governor's term in office.
Perry is the winner in this race. During his term in office, Texans' per capita income climbed from 94 to 98 percent of the U.S. average. Christie is the clear loser. Under his leadership, New Jersey per capita income slipped from 127 to 123 percent of the U.S. average.
Overall, except for Christie, it appears that the 10 present or former governors contending for the presidency were average or above-average stewards of their states' economies.
Policies enacted during a governor's term may have longer-term consequences for the state after he leaves office. For example, Walker's attack on state employee unions in Wisconsin is likely to have long-term consequences — although his defenders and detractors disagree on what those consequences will be.
Altogether, four of the presidential aspirants are still in office and three more left office recently, so it is too early to evaluate the long-term consequences of their governorships. However, three former governors (Pataki, Huckabee and Bush) have been out of office for five years or more. Five years seems a reasonable length of time over which to suppose that a governor's policies could remain a key factor, good or bad, in a state's economic results.