HIAS-E-105

An Inquiry into the Process of Upgrading Rice Milling
Service: The Case of Mwea Irrigation Scheme in Kenya
Yukichi Mano(a), Timothy Njagi Njeru(b), Keijiro Otsuka(c)(a) Hitotsubashi University(b) Tegemeo Institute of Agricultural Policy and Development, Egerton University(c) Kobe University

March, 2021

Hitotsubashi Institute for Advanced Study, Hitotsubashi University
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An Inquiry into the Process of Upgrading Rice Milling Service:
The Case of Mwea Irrigation Scheme in Kenya *March 2021
Yukichi Mano †, Timothy Njagi Njeru ‡, Keijiro Otsuka §Abstract
Countries in sub-Sahara Africa (SSA) heavily rely on rice imported from Asia, partly
because of rapidly increasing rice demand and partly because of consumers’ preference
for high-quality Asian rice. A few entrepreneurial rice millers in Kenya adopted largescale improved milling machines, including the component called destoners, around 2010,
which they learned from China. Later, smaller-sized improved machines were introduced
and more widely adopted. These adopters successfully improved the quality of milled rice,which can compete with imported rice, and their business performance. In contrast, manyother millers without adopting improved machines were forced to reduce their businessor exit the industry.
Key words: rice quality, rice milling, destoner, Kenya, sub-Sahara Africa
JEL code: Q13, Q16, Q18

This paper is a result of a research project being conducted at Japan International Cooperation
Agency – Ogata Sadako Research Institute for Peace and Development (JICA-Ogata-RI), entitled "Anempirical analysis on expanding rice production in Sub Sahara Africa." The authors are deeply
indebted to Etsuko Masuko and Sachiko Mitsumori of JICA-Ogata-RI for supporting the research
project. They also thank Takeshi Sakurai, Kazushi Takahashi, Yuko Nakano, Koji Makino and Kei
Kajisa for their valuable comments on earlier versions of this paper. We are grateful for the financial
support of JICA-Ogata-RI, Grant-in-Aid for Scientific Research on Innovative Areas-25101001 and
Grant-in-Aid for Scientific Research (A)-17H00986. The authors remain solely responsible for thecontents of this paper.
† Hitotsubashi University (yukichi.mano@r.hit-u.ac.jp)‡ Tegemeo Institute of Agricultural Policy and Development, Egerton University(tnjagi@tegemeo.org)§ Kobe University (otsuka@econ.kobe-u.ac.jp)*

11. Introduction
Countries in sub-Sahara Africa (SSA) have made serious efforts to increase domestic
staple food production to improve food security and facilitate poverty reduction,
especially after the 2007-08 food crisis. Meanwhile, rice is found to be a particularly
promising crop to increase food production in SSA (Otsuka and Larson 2012, 2016;
CARD, 2019; Otsuka, 2019). In fact, the annual growth rate of rice production was ashigh as 6.8 % between 2009 and 2019 (Soullier et al., 2020). However, rice import isestimated to be increasing more rapidly at 7.8 % per annum, and around one-third of riceconsumed in SSA is still imported from Asia, with varying degrees in various countries
ranging from 10% to 93% (Mendez del Villar and Lançon, 2015; Saito et al., 2015; FAO,
2018).
Population growth, urbanization, and increasing income raise rice consumption,
and, importantly, urban consumers generally prefer high-quality imported Asian rice overdomestic rice (Diako et al. 2010; Futakuchi et al. 2013; Demont et al. 2017; Ibrahim etal. 2020). Among many factors affecting grain quality such as varieties, cultivation,
harvesting, threshing, and storage technologies (Futakuchi, et al., 2013), it is commonlyargued that the use of inappropriate milling machines is a major reason why domestic
milled rice cannot compete with imported rice from Asia (Fiamore, et al., 2017; Ragasa,
et al., 2020). Research based on a framed field experiment demonstrates that urban
consumers are more willing to purchase rice with high levels of cleanliness and low
breakage rates of grains (Demont and Ndour, 2015; Demont et al., 2017), which suggests
the importance of appropriate rice milling. Importantly, case studies by Tokida et al.
(2014) and Kapalata and Sakurai (2020) reveal that the adoption of destoners and otherimproved milling machines allows rice millers to charge higher milling fees and increases
2their profitability in Uganda and Tanzania, respectively. However, the evidence is still
limited whether improved milling technologies enables domestic rice to compete with
imported rice.
This paper studies the development process of rice milling cluster in the largest riceproduction area in Kenya, called the Mwea irrigation scheme, which is situated 90 km
northeast of Nairobi, with 8,500 hectares of irrigated paddy area, growing primarily
improved Basmati rice, １ and achieving rice yield of 6.2 tons per hectare with two crop
cycles (Njeru et al. 2016; Kikuchi, et al., 2021). Some of these rice millers have graduallyadopted improved milling machines over the past 10 years, ２ and the rice milled by thesemillers is of higher quality and successfully competes with imported rice from Asia inurban markets, including Nairobi, the capital of Kenya. We observed supermarkets in
Nairobi selling the improved Basmati rice from Mwea at 140 to 200 Kshs per kg,
compared with Pakistani long grain at 100 to 120 Kshs per kg as of 11 December 2018. ３
These observations indicate that African rice can compete with Asian rice if improved
milling machines are introduced to SSA.
We collected the primary data of the commercial millers operating in Mwea in 2011,2016, 2018, and 2019 to analyze the adoption process of destoners and other improved
milling technologies and their effects on the quality of milling service, the businessperformance, and the survival rate in the market. Because destoners and other improved
devices used to be components of mainly large-scale multi-stage milling machines, only
Improved Basmati is cross-breed between Basmati and high-yielding modern varieties and widelygrown in India and Pakistan. It is lower quality but higher yielding than original Basmati rice. The
only small amount of other rice varieties is produced solely for farmers’ domestic consumption.
２
Improved milling machines have pre-cleaners, destoners, graders, and color sorters in addition tode-huskers and polishers, the standard functions of traditional machines (see Appendix Table).
３
The Pakistani rice is not Basmati, but some type of long grain nonaromatic rice. According to our
informal interviews with local rice traders, some sellers blended Mwea rice with imported rice from
Pakistan, and they sold it as “Mwea rice.”
１3

3 out of 82 sample millers in 2011 and 15 out of 103 millers in 2016 were using destoners.
But subsequently, small- and medium-scale multi-stage milling machines with destoners
became locally available, and 8 and 11 additional millers newly adopted destoners in 2018and 2019, respectively. By contrast, many millers without adopting improved
technologies were forced to shrink their business or exit the market. Using the doubly
robust method and the endogenous switching regression to address the endogeneity of
destoner adoption, we find that the adoption of improved rice milling technologies is
associated with higher milling fees, a greater amount of milled rice, and higher
profitability. Moreover, the millers using destoners are more likely to survive in themarket. These findings confirm the critical importance of improved rice milling
technology in enhancing the quality of African rice.
The rest of this paper is organized as follows. Section 2 explains the data anddescribes the characteristics of sample rice millers in Mwea. Section 3 postulates the
hypotheses and explains the empirical strategy, and Section 4 describes the estimation
results. Section 5 concludes the paper.

2. Millers in Mwea
Figure 1 presents changes in rice consumption, production, imports, and paddy pricein Kenya from 2010 to 2019. After the 2007-2008 food crisis, the paddy price declined
over time, consistent with the decline in the world rice price (Kikuchi et al., 2021). While
rice consumption and imports almost doubled, rice production was stagnant during thisperiod in Kenya. There was a severe drought in 2016 and 2017 in the horn of Africa region,
which may have depressed rice production in the country over this period.
The Mwea Irrigation Scheme produces 80 to 88 % of domestic rice in Kenya
4

(Samejima et al., 2020), and we study the rice millers in Mwea to inquire into thedevelopment process of the rice milling sector. We find that learning new technologies
from overseas played a crucial role in the development of rice milling. In what follows,
we would like to discuss the history of the development of the rice milling industry andexplain our primary data collection in Mwea.

2.1 Brief history
In the Mwea Irrigation Scheme, the history of modern rice milling dates back to 1967
when a public rice miller, Mwea Rice Mill Ltd. (MRM), which had a monopoly right forrice milling service, began operating four lines of large multi-stage milling machine
imported from Germany. In 1999 the rice sector was liberalized, and MRM started
competing with other millers for milling service. In early periods, operators of multi-stage
milling machines received on-the-job-training at MRM, and some moved to other millers
later.
In 2000, Mwea Rice Growers Multipurpose Cooperative Society Ltd. (MRGM)
purchased a large Chinese multi-stage milling machine without a destoner because they
did not realize its importance as they bought the machine from a broker in Nairobi without
visiting China. In 2007, a private miller, Mwega, purchased a second-hand small-sized
multi-stage milling machine with destoners. But this installation did not influence othermillers, probably because Mwega was a small miller at that time.
A significant event occurred in 2010 when the chairman and two workers of
MRGM went to China to learn new milling technologies and purchased a new multi-stage
milling machine. Notably, the new machine this time was equipped with a destoner, which
improved the quality of milled rice by removing small stones and other impurities. In the5following period, some owners of millers who had expertise in rice marketing or
accumulated wealth through other business activities also started inquiring into new rice
milling technologies by visiting machine suppliers in China. As a result, a little over 10
private millers and MRM installed large multi-stage milling machines in the first half ofthe 2010s. Aside from visiting China, these owners employed experienced operators,
especially from MRM and MRGM.
Because small- or medium-sized multi-stage milling machines were locallyintroduced from China in the late 2010s and the importance of destoners became widely
recognized in the milling cluster, other millers, particularly those highly educated, also
adopted destoners. By contrast, the other millers either reduced their business while using
traditional types of milling machines without de-stoners (so-called “Jets” and “fridges”)
or exited the market.

2.2 Data
We visited the Mwea Irrigation Scheme in 2011, 2017, and 2020 to interview thecommercial rice millers. As in other rice millers in SSA, their task is primarily to provide
milling service for farmers and traders, rather than purchasing paddy and selling milled
rice to the markets. Because December and January are the main season of rice harvesting
and milling in Mwea, our survey mainly focused on rice millers' characteristics andperformance in January 2011, December 2016, December 2018, and December 2019.
There was no official list of rice millers during our survey in 2011 and 2017, and thecoverage of the survey gradually expanded over the rounds as we discovered millers
operating in this area. In 2011, we visited the millers in Mwea town (locally known as
Wanguru or Ngurubani), stretching over 5 km along the Embu-Nairobi highway,
6connecting Mwea and Nairobi in about 1.5 hours, and in Kandongu town, which is about
4 km off the Embu-Nairobi highway. In 2017, we maintained this strategy, but we also
visited other additional mills deemed commercial on a local rice extension officer's advice.
The 2020 survey is the most comprehensive, as we compared our list of rice millers withthe list that we obtained from the county government, which had also tried to construct a
census of all rice millers in the county.

2.3 Descriptive statistics
Table 1 presents our sample millers' basic characteristics by the destoner adoption
status, representing improved rice milling technologies including pre-cleaners andgraders (see Appendix Table), as of December 2019. The survey coverage was expanded
over time, and 62 and 45 millers were added in the 2017 and the 2019 surveys,
respectively. The early adopters are the millers that adopted improved machines by 2016,
and three did so in 2011. The adoption rates were 3.7% (or 3/82) and 14.6% (or 15/103)
in 2011 and 2016, respectively. The late adopters are the millers that adopted destoners
and other improved devices after 2016. Because of their adoption, the adoption rateincreased to 26.1% (or 22/84) in 2018 and 34.7% (or 33/95) in 2019. Many millers that
did not adopt improved technologies exited the market: Between 2012 and 2016, 40 of
41 exited millers were non-adopters, while 52 of 53 exited millers between 2017 and 2019
did not have destoners and other improved devices.
The average year of the establishment was 2009, while the early and the late adopterswere established in 2005 and 2011 on average, respectively. The Embu-Nairobi highway
was constructed in 2007, and one-third of non-adopters and most adopters of improved
machines were located along the highway. The average age of main decision-makers was7

50 years old, and they were mostly male. Only 45 % of the non-adopters were high school
graduates, whereas almost all the decision-makers of adopters were high school graduates.
Many decision-makers of non-adopters were previously farmers, whereas those of
adopters have work experience in other businesses or formal jobs.
Table 2 presents the total milling capacity, the value of milling machines, and thenumber of employees. Almost all the sample rice millers had only one milling machine. ４
In 2011 when only three early adopters used destoners, the average milling capacity was
similar among three groups of rice millers. ５ From 2011 to 2016, the average capacity ofearly adopters increased significantly. In 2019, the non-adopters had a total milling
capacity of 816 kg per hour, using the traditional type of milling machine. The early
adopters had large-sized multi-stage milling machines, with a total milling capacity of
6196 kg per hour, and the late adopters installed small- or medium-sized multi-stage
milling machines, with an average milling capacity of 3479 kg per hour. ６
We also collected the milling machines' present value, measured by the decisionmaker’s willingness to pay (WTP) in 2016, 2018, and 2019 (Table 2). The non-adopters’
WTP of milling machines was 0.19 million Kshs in 2019, ７ whereas the early adopters’
WTP and the late adopters’ WTP were 13.0 million Kshs and 4.9 million Kshs,
respectively. Furthermore, the non-adopters employed only 0.5 worker on average, while
the early adopters and the late adopters employed 10 and 4 workers, respectively, in 2019

Only nine millers had two machines, and only one had three machines in 2019.
Although we visited MRM and MRGM in 2011, we did not formally interview them because theirtechnologies and business size seemed to be too distinct from other millers. We interviewed them in2017 and 2019.
６
Appendix Table presents that the areas of workshop, storage, and yard were also largest for the
early adopters, which were followed by the late adopters, and the non-adopters had the smallest
space. The early adopters attract traders by offering their large storage space free of charge.
７
In this paper, all the monetary values are deflated using the GDP deflator, and presented in thereal value of 2019. The average exchange rate in December 2019 was 101.5 Kshs to 1 USD.
４５8

(Table 2).
Table 3 presents the monthly milling performance of sample millers for January 2011,
December 2016, December 2018, and December 2019. ８ The average milling fees, which
are expected to reflect the milling quality, of the early adopters and the late adopters were2.64 Kshs per kg and 2.37 Kshs per kg in 2019, respectively, which were substantiallyhigher than the milling fee of the non-adopters of 1.76 Kshs per kg. Over time, the nonadopters’ milling fee increased from 1.89 Kshs per kg in 2011 to 2.03 Kshs per kg in 2016
but declined to 1.81 Kshs per kg in 2018 and 1.76 Kshs per kg in 2019, which is likely toreflect decreased demand for their milling service. The early adopters' milling fee
increased more substantially from 2.10 Kshs per kg in 2011 to 2.83 Kshs per kg in 2016,
when all of them adopted destoners. Similarly, the late adopters' milling fee increased
from 1.61 Kshs per kg in 2016 to 2.29 Kshs per kg in 2018 and 2.37 Kshs per kg in 2019.
We do not know why the late adopters' milling fee was as low as 1.61 Kshs per kg in 2016
when it was 2.03 Kshs per kg for the non-adopters. It may well be that their strategy was
to attract customers by reducing milling fees in the face of competition with early adopters.
As may be expected, in 2019, their average milling fee was slightly lower than that ofearly adopters.
The non-adopters’ amount of rice milled for customers declined from 52 tons in 2011
to 26 tons in 2016 and 22 tons in 2019 (Table 3). By contrast, the early adopters’ amountof milled rice increased from 109 tons in 2011 to 270 tons in 2016, when they adopted
destoners, and further to 422 tons in 2018 and 883 tons in 2019. The late adopters’ amountof milled rice also increased substantially from 56 tons in 2016 to 220 tons in 2018 andAppendix Table presents the annual amount of rice sold in 2019. We believe that the monthly data
we use are more accurate than the annual data, because the recall period is shorter.
８

9

255 tons in 2019, as they increased destoner adoption. Figure 2 presents changes in themarket share of the amount of milled rice by these three groups. In 2011, the non-adoptergroup dominated the milling service market with a market share of 80%, whereas theearly adopter group rapidly increased its market share to 62% in 2016. The late adopters
had their market share at 8% and 5% in 2011 and 2016, respectively, but their market
share sharply increased to 27% in 2018 and 26% in 2019. The non-adopters lost asignificant market share to the improved technology adopters and had only 7% of themarket share in 2019. The near demise of non-adopters strongly indicates that millingmachines with improved devices are profitable.
About 40 % of sample rice millers purchased paddy ９ and sold milled rice toconsumers, supermarkets, and traders (Table 4). The proportion of millers that sold milled
rice was similar across the three groups, and it did not change over time. Although notreported in Table 4, a few millers used brand names when they sold milled rice (e.g., four
early adopters and three late adopters in 2019). The non-adopters of destoners selling ricesold 5.2 tons in 2016, 7.0 tons in 2018, and 6.8 tons in 2019, whereas the early adoptersselling rice sold 249 tons in 2016, 302 tons in 2018 and 217 tons in 2019. The amount ofrice sold by the late adopters increased from 12 tons in 2016 to 54 tons in 2018 and 38
tons in 2019, which remain small compared to their rice milled for customers. Theseobservations suggest that some early adopters shifted their business focus to selling rice,
while the late adopters increased their share in the milling service. The non-adopters’
price of sold rice declined from 124.4 Kshs per kg in 2016 to 120.5 Kshs per kg in 2018
and 115.4 Kshs per kg in 2019, while the early adopters’ price of rice sold decreased from
141.0 Kshs per kg in 2016 to 138.2 Kshs per kg in 2018 and 131.4 Kshs per kg in 2019.

９

There is no contract farming system for rice, and these millers do not provide farmers with credit.
10The late adopters sold rice at 132.8 Kshs per kg in 2016. The price substantially increased
to 140.6 Kshs per kg in 2018 and 130.4 Kshs per kg in 2019, which became comparable
to the early adopters’ rice price. １０
We calculated the monthly capacity utilization rate to examine the milling
productivity per machine’s capacity operating for 200 hours per month (Table 5). １１ The
non-adopters reduced the capacity utilization rate over time from 0.60 in 2011 to 0.30 in
2016, 0.25 in 2018, and 0.21 in 2019, which suggests the decreased demand for the nonadopters’ milling service. The early adopters also reduced the capacity utilization ratefrom 1.33 in 2011 to 0.40 in 2016 when they initially adopted large-scale multi-stage
milling machines but could not attract many customers for milling service. However, theearly adopters increased the capacity utilization rate to 0.64 in 2018 and 1.36 in 2019
when they substantially increased the milling service, as observed in Table 3. The lateadopters initially had a high capacity utilization rate of 1.37 in 2011, which dropped to0.38 in 2016. Nevertheless, the late adopters maintained the capacity utilization rate at
0.38 in 2018 and slightly increased it to 0.45 in 2019, unlike the declining performanceof the non-adopters. This monthly capacity utilization rate reflects the milling
performance in the main season. We also calculated the annual capacity utilization rate in2019 (Appendix Table) and found that the non-adopters had 0.28 and the late adopters
had 0.45, comparable to their performance in the main season, whereas the early adopters
Paddy quality is also important in determining the overall rice quality, and farm level agronomy
affects the quality of paddy, including levelling, fertilizer application, amount of water during crop
establishment and pest and disease control. Mechanical harvesting has also helped reduce the losses.
Traders determine the quality of paddy through observation and checking for moisture content. Many
traders have moisture meters and usually check for the moisture content at the time of purchasing. We
do not observe a significant difference in the minimum required moisture content across millers(Appendix Table). They also observe the paddy grain to ensure that the pods are full, which is a signof good quality paddy. But there is no grading system or pricing differential on paddy quality.
１１
The monthly capacity utilization rate is the total amount of milled rice and sold rice (tons permonth) divided by the milling capacity of machines for 200 hours of operation (tons per month).
１０

11

had only 0.13. This result suggests that the early adopters could not attract manycustomers and substantially reduced their milling performance in the offseason, leaving
their large-scale milling machines idle.
The profit of the non-adopters was negative, -0.08 million Kshs in 2016, -0.05
million Kshs in 2018, and -0.08 million Kshs in 2019 (Table 5). １２ The early adopters'
profit was far the largest but declined from 11.5 million Kshs in 2016 to 10.3 million Kshs
in 2018 and 2.84 million Kshs in 2019 (Table 5). By contrast, the late adopters' profit
substantially increased from 0.03 million Kshs in 2016 to 1.04 million Kshs in 2018 and2.64 million Kshs in 2019, as they upgraded the milling machines. Since the absoluteamount of profit depends on the amount of investment, we also calculated the ratio of
profit to milling capacity per month as an alternative indicator of the milling business's
profitability. The non-adopters had -0.04 in 2016, -0.01 in both 2018 and 2019. The early
adopters also had negative and declining ratios, -0.001 in 2016, -0.02 in 2018, and -0.20
in 2019, １３ suggesting overcapacity for early adopters, particularly after the late adopters
also adopted the improved milling machines. In contrast, although the late adopters
initially had a negative ratio of -0.03 in 2016, they increased the profit per capacity to
0.12 in both 2018 and 2019.

We calculated profit by subtracting labor cost, purchasing cost of paddy, electricity cost, andmaintenance cost and depreciation cost of milling machines from the revenue of milling service andselling rice and bran. The depreciation cost is estimated by assuming the linear depreciation over theusable lifetime, D = (V-S)/(12 x L), where D = monthly depreciation, V = the value of machine, S =the salvage value of the machine after its useful use, assumed to be 10 % of the machine value, L =useful life of the milling machine, assumed to be 10 years (Tokida et al., 2014; Norbu, 2018). The
estimation results below are essentially robust to parameter values in reasonable ranges. Because of
the data limitation, we did not consider other expenses such as rent of workspace and storage,
marketing cost, or tax payment.
１３ The early adopters’ average profits are positive because of large positive profits of some millers
using large milling machines despite negative profits of other millers. But the average profit-capacity
ratios reduce the weight for those large millers and turned out to negative.
１２

12

3. Hypotheses and Empirical strategy
3.1 Hypotheses
Because, in the early 2010s, the importance of the destoner component was not widely
known and the improved technologies were available primarily with the large-sized multistage milling machines, which were expensive, the early adopters are expected to beknowledgeable about the urban rice market and to have sufficient wealth to make a large
initial investment. By the time when the small- and medium-sized multi-stage millingmachines became available in the late 2010s, the importance of special knowledge about
the marketing of high-quality rice and wealth would have reduced. Instead, the generalhuman capital represented by education is expected to play a larger role in making proper
adoption decisions of milling machines. Moreover, because the millers operating along
the highway can attract more large urban traders keen on procuring high-quality milled
rice, they have a greater incentive to improve their milling quality. Based on these
considerations, we would like to hypothesize that:

Hypothesis 1: “Those who had acquired knowledge about urban rice market or
accumulated wealth through former occupations tended to adopt improved milling
technologies early, whereas those highly educated tended to adopt improved technologies
later. Moreover, the millers along the highway were more likely to adopt improved
technologies.”

As we have learned in the previous section, because the improved milling
technologies were available primarily for large-sized multi-stage milling machines in theearly 2010s, these early adopters are expected to provide a higher quality of milling13

service and market performance in those years. In the late 2010s, small- and mediumsized multi-stage milling machines were introduced in Mwea, which reduced theadvantage in high-quality milling service of the early adopters. Moreover, the descriptive
analyses above suggest the overcapacity for the early adopters, and, hence, theproductivity and profitability of the early adopters' business may have been lower thanthe late adopters. Based on these observations, we would like to hypothesize that:

Hypothesis 2: “Both the early and the late adopters improved the milling quality withimproved milling technologies, but the late adopters outperformed the early adopters in
productivity and profitability because of the excess capacity of the early adopters’ millingmachines.”

Furthermore, during the 2010s, millers who adopted improved machines are
expected to have improved their milling and overall business performance. In contrast,
the other millers kept using traditional milling machines and performed poorly or exitedthe market because they lost the milling service business to the adopters. Thus, we also
would like to test the following hypothesis,

Hypothesis 3: “The non-adopters tended to exit the market because they lost milling
service business to the adopters of improved machines, who were more likely to survive
in the business.”

3.2 Doubly Robust and Endogenous Switching Regression
We consider an estimation strategy to explicitly control the selection on observables
14and match millers with similar characteristics. The studies on agricultural technologies
use such estimation methods, including propensity score matching, inverse probability
weighting, and the doubly robust (DR) method, when no plausible instruments areavailable (Takahashi and Barrett, 2014; Bellemare and Novak, 2016; Kahn, et al., 2019;
Mano et al., 2020). We apply the DR method, or more precisely, inverse-probability
weighted regression adjustment, which combines the regression and propensity scoreweighting. It is more robust than the propensity score matching estimator and the inverseprobability-weighting estimator and can provide a consistent estimator as long as either
the propensity score for destoner use or the outcome regression in terms of miller’scharacteristics is correctly specified (Wooldridge 2007; Wooldridge 2010, Section
21.3.4). １４ More specifically, we first estimate the binary response model of improved
technology adoption,′𝛽𝛽 + 𝜖𝜖𝑖𝑖𝑖𝑖 with 𝐷𝐷𝑖𝑖𝑖𝑖 = �
𝐷𝐷𝑖𝑖𝑖𝑖∗ = 𝑥𝑥𝑖𝑖𝑖𝑖

1 𝑖𝑖𝑖𝑖 𝐷𝐷𝑖𝑖𝑖𝑖∗ > 0
0 𝑖𝑖𝑖𝑖 𝐷𝐷𝑖𝑖𝑖𝑖∗ ≤ 0(1)

where 𝐷𝐷𝑖𝑖𝑖𝑖∗ is the latent variable of improved technology adoption, 𝑥𝑥𝑖𝑖𝑖𝑖 is the vector ofmiller i’s characteristics in a month of main season in year t = 2011, 2016, 2018, 2019,
𝛽𝛽 is the parameter to be estimated, 𝜖𝜖𝑖𝑖𝑖𝑖 is the error term, and the probability of improved

technology adoption conditional on the miller’s characteristics can be expressed as the
probit model,′
𝑃𝑃(𝐷𝐷𝑖𝑖𝑖𝑖 = 1|𝑥𝑥𝑖𝑖𝑖𝑖 ) = Φ(𝑥𝑥𝑖𝑖𝑖𝑖𝛽𝛽) ≡ 𝑝𝑝(𝑥𝑥𝑖𝑖𝑖𝑖 )where 𝑝𝑝(𝑥𝑥𝑖𝑖𝑖𝑖 ) is the propensity score of improved technology adoption. The miller’scharacteristics are decision-makers' age, the high school dummy that takes 1 if thedecision-maker graduated from high school, the former occupation dummies, and the rice
miller's establishment year. The year dummies are also used. Using the estimated１４

We used STATA command teffects ipwra to implement the DR method.
15

propensity 𝑝𝑝̂ (𝑥𝑥𝑖𝑖𝑖𝑖 ), we estimate the regression parameters 𝛾𝛾’s by using the following setof the inverse probability weighting linear least squares problems,′min � � 𝐷𝐷𝑖𝑖𝑖𝑖 (𝑌𝑌𝑖𝑖𝑖𝑖 − 𝑥𝑥𝑖𝑖𝑖𝑖
𝛾𝛾1 )2⁄𝑝𝑝̂ (𝑥𝑥𝑖𝑖𝑖𝑖 )
𝛾𝛾1

𝑖𝑖

𝑡𝑡

′
min � � (1 − 𝐷𝐷𝑖𝑖𝑖𝑖 )(𝑌𝑌𝑖𝑖𝑖𝑖 − 𝑥𝑥𝑖𝑖𝑖𝑖
𝛾𝛾0 )2⁄[1 − 𝑝𝑝̂ (𝑥𝑥𝑖𝑖𝑖𝑖 )]
𝛾𝛾0

𝑖𝑖

𝑡𝑡

We estimate the average treatment effect on the treated (ATT) of the improved technology
adoption on outcome 𝑌𝑌 as the average of the difference in predicted values of outcomes,
𝜏𝜏̂𝐴𝐴𝐴𝐴𝐴𝐴,𝐷𝐷𝐷𝐷 = 𝑥𝑥̅1′ (𝛾𝛾�1 − 𝛾𝛾�0 )(2)where ���𝑥𝑥1 = 𝑛𝑛1−1 ∑𝑖𝑖 ∑𝑡𝑡 𝐷𝐷𝑖𝑖 𝑥𝑥𝑖𝑖𝑖𝑖 is the vector of average characteristics of millers (including

the constant term) over the improved technology adopters and 𝑛𝑛1 is the number of

improved technology adopters. Here, 𝜏𝜏̂𝐴𝐴𝐴𝐴𝐴𝐴,𝐷𝐷𝐷𝐷 is the DR estimator of ATT. The outcome

variables are the milling fee, the amount of rice milled for customers, the rice purchasing
and selling dummy, which takes 1 if the miller purchased paddy and sold rice and 0
otherwise, the price of sold rice, the amount of sold rice, the capacity utilization rate, thegross profit, the gross profit per capacity, and the survival dummy, which takes 1 if themiller continued operation until the next period of our observation and 0 otherwise.
The other empirical strategy that we use is the endogenous switching regression(ESR), and this method is also often used in the studies of technology adoption inagriculture to address the endogeneity bias due to unobserved characteristics, which isassumed away by the doubly robust method (Di Falco, et al., 2011; Konje et al., 2018;
Bairagi, et al., 2020). The first step is to estimate the binary response model of improved
technology adoption (1), and the second step specifies the relationship between theoutcome variable 𝑌𝑌𝑖𝑖𝑖𝑖 and a vector of miller’s characteristics 𝑥𝑥𝑖𝑖𝑖𝑖 for improved

technology adopters and non-adopters, separately,16

Destoner adopters:
Nonadopters:′
𝑌𝑌1𝑖𝑖𝑖𝑖 = 𝑥𝑥1𝑖𝑖𝑖𝑖
𝛿𝛿1 + 𝜇𝜇1𝑖𝑖𝑖𝑖 if 𝐷𝐷𝑖𝑖𝑡𝑡 = 1′
𝑌𝑌0𝑖𝑖𝑖𝑖 = 𝑥𝑥0𝑖𝑖𝑖𝑖
𝛿𝛿0 + 𝜇𝜇0𝑖𝑖𝑖𝑖 if 𝐷𝐷𝑖𝑖𝑖𝑖 = 0

(3)
(4)

where subscripts 1 and 0 represent adopters and non-adopters, respectively, 𝛿𝛿’s are thevectors of regression coefficients, and 𝜇𝜇’s are the random error terms. The error terms inequations (1), (3), (4) are assumed to be jointly and normally distributed with mean vector
zero and the following covariance matrix:
𝜎𝜎𝜖𝜖2
Ω = 𝑐𝑐𝑐𝑐𝑐𝑐(𝜖𝜖𝑖𝑖𝑖𝑖 , 𝜇𝜇1𝑖𝑖𝑖𝑖 , 𝜇𝜇0𝑖𝑖𝑖𝑖 ) = �𝜎𝜎𝜖𝜖1
𝜎𝜎𝜖𝜖0

𝜎𝜎𝜖𝜖1
𝜎𝜎12
∙

𝜎𝜎𝜖𝜖0
∙ �
𝜎𝜎02

where 𝜎𝜎𝜖𝜖2 = 𝑣𝑣𝑣𝑣𝑣𝑣(𝜖𝜖𝑖𝑖𝑖𝑖 ) = 1 , 𝜎𝜎12 = 𝑣𝑣𝑣𝑣𝑣𝑣(𝜇𝜇1𝑖𝑖𝑖𝑖 ) , 𝜎𝜎02 = 𝑣𝑣𝑣𝑣𝑣𝑣(𝜇𝜇0𝑖𝑖𝑖𝑖 ) , 𝜎𝜎𝜖𝜖1 = 𝑐𝑐𝑐𝑐𝑐𝑐(𝜖𝜖𝑖𝑖𝑖𝑖 , 𝜇𝜇1𝑖𝑖𝑖𝑖 ) ,𝜎𝜎𝜖𝜖0 = 𝑐𝑐𝑐𝑐𝑐𝑐(𝜖𝜖𝑖𝑖𝑖𝑖 , 𝜇𝜇0𝑖𝑖𝑖𝑖 ), and the covariance between 𝜇𝜇1𝑖𝑖𝑖𝑖 and 𝜇𝜇0𝑖𝑖𝑖𝑖 are not defined because
they are not observed simultaneously (Green, 2012). The conditional expectation of theoutcome of the destoner adopters in the actual case of adopting destoners can be expressedas′′
𝐸𝐸(𝑌𝑌1𝑖𝑖𝑖𝑖 |𝐷𝐷𝑖𝑖𝑖𝑖 = 1, 𝑥𝑥1𝑖𝑖𝑖𝑖 ) = 𝑥𝑥1𝑖𝑖𝑖𝑖
𝛿𝛿1 + 𝐸𝐸(𝜇𝜇1𝑖𝑖𝑡𝑡 |𝐷𝐷𝑖𝑖𝑖𝑖 = 1, 𝑥𝑥1𝑖𝑖𝑖𝑖 ) = 𝑥𝑥1𝑖𝑖𝑖𝑖
𝛿𝛿1 + 𝜎𝜎𝜖𝜖1 𝜆𝜆1𝑖𝑖𝑖𝑖(5)

𝜙𝜙�𝑥𝑥 ′ 𝛽𝛽�

where 𝐸𝐸(𝜇𝜇1𝑖𝑖𝑖𝑖 |𝐷𝐷𝑖𝑖𝑖𝑖 = 1, 𝑥𝑥1𝑖𝑖𝑖𝑖 ) = 𝜎𝜎𝜖𝜖1 Φ�𝑥𝑥1𝑖𝑖𝑖𝑖′ 𝛽𝛽� ≡ 𝜎𝜎𝜖𝜖1 𝜆𝜆1𝑖𝑖𝑖𝑖 . Analogously, the conditional
1𝑖𝑖𝑖𝑖

expectation of the outcome of the destoner adopters in the counterfactual case of not
adopting destoners can be expressed as′′
𝐸𝐸(𝑌𝑌0𝑖𝑖𝑖𝑖 |𝐷𝐷𝑖𝑖𝑖𝑖 = 1, 𝑥𝑥1𝑖𝑖𝑖𝑖 ) = 𝑥𝑥1𝑖𝑖𝑖𝑖
𝛿𝛿0 + 𝐸𝐸(𝜇𝜇0𝑖𝑖𝑖𝑖 |𝐷𝐷𝑖𝑖𝑖𝑖 = 1, 𝑥𝑥1𝑖𝑖𝑖𝑖 ) = 𝑥𝑥1𝑖𝑖𝑖𝑖
𝛿𝛿0 + 𝜎𝜎𝜖𝜖0 𝜆𝜆1𝑖𝑖𝑖𝑖(6)

Following Heckman et al. (2001) and Di Falco et al., (2011), we calculate the covariatespecific effect of the treatment on the treated as the difference between equations (5) and(6),′(𝛿𝛿1 − 𝛿𝛿0 ) + (𝜎𝜎𝜖𝜖1 − 𝜎𝜎𝜖𝜖0 )𝜆𝜆1𝑖𝑖𝑖𝑖
𝐸𝐸(𝑌𝑌1𝑖𝑖𝑖𝑖 |𝐷𝐷 = 1, 𝑥𝑥1𝑖𝑖𝑖𝑖 ) − 𝐸𝐸(𝑌𝑌0𝑖𝑖𝑖𝑖 |𝐷𝐷 = 1, 𝑥𝑥1𝑖𝑖𝑖𝑖 ) = 𝑥𝑥1𝑖𝑖𝑖𝑖

Taking the average of this value over the destoner adopters, we obtain the ATT estimatorof the destoner adoption using the endogenous switching regression,17𝜏𝜏̂𝐴𝐴𝐴𝐴𝐴𝐴,𝐸𝐸𝐸𝐸𝐸𝐸 = 𝑥𝑥̅1′ �𝛿𝛿̂1 − 𝛿𝛿̂0 � + (𝜎𝜎�𝜖𝜖1 − 𝜎𝜎�𝜖𝜖0 )𝜆𝜆̅1where ���𝑥𝑥1 = 𝑛𝑛1−1 ∑𝑖𝑖 ∑𝑡𝑡 𝐷𝐷𝑖𝑖 𝑥𝑥𝑖𝑖𝑖𝑖 is the vector of average characteristics of millers (including

the constant term) over the destoner adopters, 𝜆𝜆1̅ is the average inverse mill’s ratio
calculated using the regression parameter estimated in model (1), 𝛿𝛿 ’s and 𝜎𝜎 ’s areparameters of regression (5) and (6) to be estimated. １５ Because we do not have a decent

instrument for destoner adoption, we rely on the nonlinearity of the inverse mill’s ratio
for the identification in parameter estimation (Wooldridge, 2010). Analogously, we also
estimate the average treatment effect on the untreated (ATUT), the hypothetical effect of
adopting improved technologies for non-adopters,𝜏𝜏̂𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴,𝐸𝐸𝐸𝐸𝐸𝐸 = 𝑥𝑥̅0′ �𝛿𝛿̂1 − 𝛿𝛿̂0 � + (𝜎𝜎�𝜖𝜖1 − 𝜎𝜎�𝜖𝜖0 )𝜆𝜆̅0

where 𝑥𝑥���0 = 𝑛𝑛0−1 ∑𝑖𝑖 ∑𝑡𝑡(1 − 𝐷𝐷𝑖𝑖 )𝑥𝑥𝑖𝑖𝑖𝑖 is the vector of average characteristics of millers(including the constant term) over the non-adopters, 𝜆𝜆̅0 is the average inverse mill’s ratio

for non-adopters. We use ATUT estimates to examine whether non-adopters had lower
expected profitability, which may be why they did not adopt improved technologies.

4. Estimation Results
Table 6 presents the estimation results of the probit model of improved technology
adoption, represented by destoner adoption, in 2011, 2016, 2018, and 2019, respectively.
We combine the early adopters and the late adopters to create a destoner adopter category
to enable the analyses with the limited sample size. The estimated effect of the highway
dummy was strictly significant, and its magnitude increased gradually over time from
0.16 in 2011 to 0.35 in 2019. In 2016, when the early adopters adopted destoners, themain decision-makers of the destoner adopters were found to have former work

１５

We used STATA command movestay to implement the ESR method.
18

experience in rice milling and trading or other business and formal jobs. In 2018 and 2019,the main decision-makers of the destoner adopters were found to have higher education
but less previous work experience in the rice market. These results are consistent with
Hypothesis 1.
Table 7 presents the estimation results of the DR method and the ESR method, and
the ATT estimates of improved technology adoption are similar between the two methods.
We also estimated the ATT for early adopters and late adopters separately using the DR
method and the ATUT of improved technology adoption using the ESR method. The
adoption of improved milling technologies increased the milling fee by 0.77 Kshs per kg
or 2.00 Kshs per kg for the adopters in general, 0.84 Kshs per kg for the early adopters,
and 0.73 Kshs per kg for the late adopters, while it would have also increased the milling
fee of the non-adopters by a smaller magnitude of 0.47 Kshs per kg if they adopted theimproved machines. These findings are consistent with the first part of Hypothesis 2. The
improved machine adoption also increased the amount of rice milled for customers by
334.9 tons or 357.3 tons for the adopters in general, 431.4 tons for the early adopters,
163.3 tons for the late adopters, while it would have also increased the amount of milled
rice for the non-adopters by a greater magnitude of 730.7 tons.
The DR estimates of ATT of improved technology adoption on the probability ofselling rice were not statistically significant. Nevertheless, according to the corresponding
ESR estimate, the improved technology adoption increased the probability of selling rice
by 0.21 for the adopters, whereas it would have reduced the probability of selling rice forthe non-adopters. The adoption of improved machines increased the price of sold rice by
10.64 Kshs per kg or 16.92 Kshs per kg for the adopters in general, 4.40 Kshs per kg forthe early adopters, which is insignificant, 17.57 Kshs per kg for the late adopters, which19

is strictly significant, whereas it would have reduced by 26.56 Kshs per kg for the nonadopters. We do not know why the adoption of improved milling machines would
decrease the non-adopters’ price of sold rice. We suspect that because the decision-makersof the non-adopters lack former work experience in rice marketing or general education,
they were incapable of increasing the rice price simply by adopting improved machines.
These findings are consistent with the first part of Hypothesis 2. The adoption of
improved technologies increased the amount of sold rice by 143.5 tons or 107.4 tons forthe adopters in general, 236.6 tons for the early adopters, 36.7 tons for the late adopters,
whereas it would have reduced by 8.1 tons for the non-adopters.
The adoption of improved machines increased the capacity utilization rate by 0.36
or 0.07 for the adopters in general, 0.46 for the early adopters, 0.20 for the late adopters,
and it would have also increased by 0.72 for the non-adopters. The DR estimates of theeffect of improved machine adoption on profit were not statistically significant. However,according to the ESR estimates, the improved technology adoption increased the profit
by 6.93 million Kshs for the adopters and would have reduced the profit substantially55.49 million Kshs for the non-adopters. As was explained earlier, because the decisionmakers of the non-adopters lack former work experience in rice marketing or general
education, we suspect that they were incapable of increasing the profit simply by adopting
improved machines. The estimated effect of improved machine adoption on the early
adopters’ profit-capacity ratio was insignificant but -0.08, suggesting the early adopters'
excess capacity. In contrast, the adoption of improved machines significantly increased
the late adopters' profit-capacity ratio by 0.14. According to the ESR estimates, theadoption of improved technologies increased the profit per capacity by 0.17 for the
adopters in general, but it would have reduced the profit-capacity ratio by 0.14 for the20

non-adopters. These findings are consistent with Hypothesis 2.
We also estimated the ATT and ATUT of destoner adoption on the millers’ survival
rate. The adoption of improved technologies increased the probability of survival until
the next period of our observation by 0.34 or 0.40 for the early adopters, and it would
have also increased the survival probability substantially for the non-adopters. １６ This
result is consistent with Hypothesis 3.

5. Concluding remarks
SSA heavily relies on rice imported from Asia to meet the rapidly increasing riceconsumption due to population growth and urbanization, despite the governments’ effort
to improve food security by increasing rice farming productivity. Consumers, especiallyin urban markets, generally prefer high-quality imported rice over domestic rice, and theprice difference is often substantial. Thus, it is commonly argued that African rice cannot
compete with Asian rice. Interestingly, however, this is not the case in the case of Mwea
rice, which is higher quality than imported Pakistani rice and, hence, more expensive.
This study explored why this happened.
This study found that learning improved milling technologies from abroad
triggered the rice milling industry's transformational improvement in the largest riceproduction area, Mwea, in Kenya. After the 2007-2008 food crisis, a few owners of rice
millers with expertise in rice marketing and accumulated wealth through other businesses
visited China and learned the importance of destoners and other improved rice millingmachines in improving the quality of milled rice. They adopted large-scale multi-stage

Because we observed the late adopters’ complete technology adoption only in the 2019 survey,
we cannot estimate their effect on survival.

１６21

rice milling machines with destoners and other improved technologies in the first half ofthe 2010s and successfully enhanced the milling quality of rice and business performance.
In the late 2010s, small- and medium-scale multi-stage rice milling machines wereintroduced to Mwea by followers, and improved rice milling technologies were more
widely adopted in the cluster, contributing to Mwea rice's competitiveness against
imported rice in the market. These findings strongly indicate the critical importance oflearning new useful knowledge from abroad for improving the performance of small
enterprises in SSA.
These findings may have significant implications for other SSA countries
struggling to improve the quality of milled rice. The critical point is that the introductionof small- and medium-scale multi-stage rice milling machines reduced the financial
burden on potential adopters and thereby assisted the wide-spread adoption of the newtechnology. In other words, the choice of appropriate technology is likely to be of crucial
importance for SSA because the profitability of investment in improved machines varies
and may not always be positive. To the extent that knowledge of various improved millingmachines is a local public good, there is room for the government to provide appropriate
information about the cost and benefit of various rice milling machines. Furthermore, wemust note that although the adoption of improved milling machines significantly
improved the quality of rice and the performance of millers in Mwea, paddy produced in
Mwea is a high-quality improved Basmati type which is uncommon in SSA. Whether the
adoption of milling machines with destoners will enhance the quality of milled rice andmillers' performance in areas where more popular rice varieties are grown is a criticalissue to be explored in future studies.

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26

Table 1. Basic characteristics of sample millers in 2019 by destoner adoptiona
Total

Nonadopters

Early adoptersb

Late adoptersc

82
(3.7)
103
(14.6)
84(26.1)
95(34.7)

72
(0)
82
(0)
57
(0)
62
(0)

6
(50)
15
(100)
14
(100)
14
(100)

4
(0)
6
(0)
13
(61.5)
19(100)

2012-2016

41

40

1

0

2017-2019

53

52

1

0

2008.92008.92005.42011.4

(8.8)

(6.3)

(12.6)(11.6)

0.52

0.33

0.92

0.84

49.8

50.4

49.7

47.8

(10.4)(10.9)(10.8)(8.6)

Female (=1)

0.31

0.33

0.21

0.31

High school/above (=1)

0.61

0.45

1

0.84

Farmer (=1)

0.38

0.43

0.21

0.32

Rice milling & trading (=1)

0.17

0.22

0.14

0.05

No. of millers(% destoner adoption)
2011
2016
2018
2019
Exit

Establishment year
On the highway (=1)
Characteristics of decision-maker
Age

Former occupation

Business & formal jobs (=1)
0.35
0.22
0.64
0.58
Mechanic (=1)
0.10
0.13
0
0.05
a. Standard deviations of continuous variables are in parentheses. The survey coverage
was expanded over time, and 62 and 45 millers were added in the 2016 and the 2019
surveys, respectively.
b. The early adopters are the millers that adopted destoners by 2016, and three of themdid so in 2011.
c. The late adopters are the millers that adopted destoners only after the 2016 survey,
and eight of them did so in 2018.
27

Table 2. Total milling capacity, WTP of milling machines, the number of employees ofmillers by destoner adoption
Total

Nonadopter

Early adopter

Late adopter

468.8

472.6

445.0

435.0

(227.9)(237.5)(89.1)(225.7)1139.0538.04453.3966.6(3032.2)(385.3)(7175.7)(581.9)2088.8819.86196.42838.4(4377.6)(575.2)(8328.0)(4710.2)

2076.7815.96196.43478.9(4298.7)(574.3)(8327.9)(5113.0)

2.15

0.27

13.0

0.44

(6.44)(0.15)(12.3)(0.27)

2018

3.19

0.19

13.5

4.4

2019

(8.11)
3.02(0.09)
0.19(14.1)
13.0

(7.1)
4.9

(7.34)(0.10)(13.5)

(6.2)

1.5

1.4

3.0

1.0

(1.4)

(1.1)

(3.3)

(0)

1.6

0.90

5.4

1.3

(2.9)

(0.63)

(6.1)

(0.5)

2.6

0.61

10.4

3.1

(10.3)(1.19)(25.3)

(5.3)

2.6

0.54

10.0

3.8

(10.4)(0.73)(25.3)(5.7)

Capacity (kg/hour)
2011
2016
2018
2019

WTP (million Kshs)
2016

Employees
2011
2016
2018
2019

Notes. Standard deviations are in parentheses. The total capacity of and the willingnessto-pay for all the milling machines at millers are reported.

28

Table 3. Monthly performance of milling service by destoner adoption
Milling fee (Kshs/kg)
2011
2016
2018
2019

Rice milled for customers (tons)
2011
2016
2018
2019

Total

Nonadopter

Early adopter

Late adopter

1.90(0.28)
2.12(1.18)
2.06(0.62)
2.01(0.57)

1.89(0.27)
2.03(1.27)
1.81(0.52)
1.76(0.46)

2.10(0.42)
2.83(0.54)
2.78(0.26)
2.64(0.39)

1.87(0.19)
1.61(0.42)
2.29(0.59)
2.37(0.42)

58.6(50.2)
65.4(163.3)130.0(293.5)198.4(791.2)51.8(48.9)
26.3(38.8)
32.3(65.5)
21.6(38.3)

108.7(30.7)
270.3(351.0)422.3(539.7)882.9(1839.9)

99.7(39.4)
55.6(11.6)
220.3(287.7)255.1(507.2)Note. Standard deviations are in parentheses. The milling fee is deflated with the GDP
deflator (the 2019 value).

29

Table 4. Monthly performance of rice sales by destoner adoption
Sell milled rice (=1)
2016
2018
2019
Sold rice (tons)
2016
2018
2019

Price of sold rice (Kshs/kg)
2016
2018
2019

Total

Nonadopter

Early adopter

Late adopter

0.38
0.41
0.42

0.37
0.44
0.41

0.40
0.36
0.35

0.50
0.37
0.47

16.4
(142.7)21.9(126.5)16.8(83.8)

5.2
(6.6)
7.0
(7.6)
6.8
(8.8)

248.6
(588.5)301.8(515.6)216.8(323.2)

12.1
(9.5)
54.1
(35.9)
38.0(49.4)

127.5(22.9)
126.4(16.3)
120.8(15.4)

124.4(24.7)
120.5(10.5)
115.4
(9.1)

141.0
(6.9)
138.2
(17.7)
131.4(18.3)

132.8(14.0)
140.6(22.2)
130.4(5.1)

Note. Standard deviations are in parentheses. The rice price is deflated with the GDP
deflator (the 2019 value).

30

Table 5. Monthly capacity utilization rate, gross profit, gross profit per capacity by
destoner adoption
Total

Nonadopter

Early adopter

Late adopter

0.70

0.60

1.33

1.37

(0.57)(0.50)(0.67)(0.65)

0.32

0.30

0.40

0.38

(0.35)(0.37)(0.26)(0.14)

0.34

0.25

0.64

0.38

(0.45)(0.33)(0.73)(0.35)

0.52

0.21

1.36

0.45

(1.65)(1.36)(3.03)(0.58)

1.71

-0.08

11.5

0.03

(18.9)(0.49)(48.3)(0.87)

1.99

-0.05

10.3

1.04

(18.1)(0.23)(42.7)(2.90)

0.92

-0.06

2.84

2.64

(11.3)(0.20)(27.6)(9.0)

Profit per Capacity (million
Kshs/kg)
2016
-0.03

-0.04

0.001

-0.03

(0.22)(0.20)(0.35)(0.17)

0.01

-0.01

-0.02

0.12

(0.20)(0.08)(0.34)(0.31)

-0.01

-0.01

-0.20

0.12

(0.36)(0.09)(0.75)(0.45)

Capacity utilization rate
2011
2016
2018
2019

Profit (million Kshs)
2016
2018
2019

2018
2019

Note. Standard deviations are in parentheses. The profit is deflated with the GDP deflator(the 2019 value). Capacity utilization rate is the ratio between the total amount of milled
rice and sold rice (tons per month) to the milling capacity of 200 hours of operation (tonsper month). Profit per capacity is the ratio between the profit (million Kshs per month) tothe milling capacity of 200 hours of operation (kg per month).

31

Table 6. Determinants of Improved Technology Adoption (Probit)
2011
2016
2018
Age

2019

0.005***

0.001-0.004-0.003(0.002)(0.003)(0.004)(0.003)

-0.03

0.005

0.21**

0.22***(0.03)(0.06)(0.10)(0.08)

0.13

0.23***-0.11-0.18*(0.09)(0.09)(0.11)(0.09)---

0.23***

0.09

0.06

(0.06)(0.10)(0.09)

0.21**-1.10**-0.28**(0.10)(0.15)(0.12)

---

---

---

-0.0006-0.0010.00003

0.003(0.002)(0.003)(0.004)(0.003)0.16**

0.23***

0.24***

0.35***(0.06)(0.07)(0.07)(0.04)

Log pseudo-likelihood-4.267-29.63-31.86-33.90

Obs.

81

103

82

93

High school
Rice miller & trading
Business & formal jobs
Mechanic
Other occupation---0.12***(0.03)

Year of establishment
Highway

Notes. The marginal effects are reported. The numbers in parentheses are robust standard
errors. ***, **, * indicate statistical significance at the 1, 5, 10% levels, respectively.

32

Table 7. Effects of Improved Milling Technologies (Doubly Robust & Endogenous Switching Regression)
Milling Fee Rice milled
Sell
Price of
Rice soldCapacity
Profit (mill.
Profit per(Kshs/kg)(ton)
milledrice(ton)util. rate
Kshs)
Capacity
rice(Kshs/kg)(million(=1)
Kshs/kg)

Survival(=1)

Doubly Robust
ATT
Early adopter’s ATT
Late adopter’s ATT

0.77***

334.9***-0.04

10.64**

143.5**

0.36**

5.93

0.01

0.34***(0.09)(147.7)(0.10)(4.34)(62.4)(0.17)(3.76)(0.06)(0.12)

0.84***

431.4***

-0.12

4.40

236.6**

0.46*

8.03

-0.08

---

(0.12)(160.4)(0.11)(5.95)(111.4)(0.26)(5.92)(0.08)

0.73***

163.3*-0.04

17.57***

36.7***

0.20**

2.20

0.14*

(0.12)(98.1)(0.10)(5.23)(9.9)(0.12)(1.46)(0.07)

2.00***

357.3***

0.21***

16.92***

107.4***

0.07*

6.93***

0.22***

0.40***(0.03)(34.5)(0.02)(1.18)(18.9)(0.04)(2.33)(0.01)(0.03)

0.47***

730.7***-1.41***-26.56***-8.1***

0.72***-55.49***-0.10***

1.32***(0.02)(9.47)(0.02)(0.38)(4.4)(0.02)(1.04)(0.004)(0.02)---

Endogenous Switching
ATT
ATUT

Notes. Robust standard errors are in parentheses. ***, **, * indicate statistical significance at the 1, 5, 10% levels, respectively.
The miller’s characteristics are also controlled in the analyses: the age of decision-makers; the high school dummy, whichtakes 1 if the decision-maker graduated from high school; the former occupation dummies; the establishment year of the rice
miller; and the year dummies.

33

Figure 1. Rice consumption, production, imports, and paddy price in Kenya
800,00090

700,000

80
70

600,000

Tons

50

400,000

40

300,000(Sh/Kg)60

500,000

30

200,000

20

100,000

10

-

-

2010

2011

Consumption (tons)

2012

2013

2014

2015

Production (tons)

Source: Kenya National Bureau Statistics 2020.

34

2016

2017

Imports (tons)

2018

2019

Price (Ksh/kg)

Figure 2. Market Share of Rice Milled for Customers by Destoner Adoption
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%

2011

2016
Non-adopters

2018
Early adopters

2019
Late adopters

Note. The early adopters are the millers that adopted destoners by 2016, and three ofthem did so in 2011. The late adopters are the millers that adopted destoners only after
the 2016 survey.

35

Appendix Table. Other characteristics of millers in 2019 by destoner adoption
Nonadopter

Early adopter

Late adopter

Pre-cleaner

0

0.93

1

De-husker

1

1

1

Polisher

0.98

1

1

Grader

0.03

0.93

0.68

Color sorter

0

0.57

0.11

Area of workshop & storage (m2)262.5

2595.2949.4(336.0)(2470.3)(898.6)23.9

3801.5553.6(69.9)(6076.3)(1813.6)

Milled rice to paddy ratio (%)

62.0

65.7

64.1

The minimum moisture content (%)(3.56)
12.6
(1.1)

(3.8)
12.0
(1.2)

(2.7)
12.9
(0.8)

Price of bran sold (Kshs/kg)

5.7

12.9

12.0

(3.1)

(2.7)

(3.3)

37.1

196.9

280.2

(253.5)(521.9)(1097.2)

The annual amount of rice milled (tons)

136.2

3766.612353.2

The annual amount of rice sold (tons)(203.3)37.7(5222.8)3355.4(46901.1)
156.2(74.7)(7072.9)(214.3)

0.28

0.13

0.45

(0.28)(0.23)(0.50)

Functions of milling machines (=1)

2Area of yard (m )The annual amount of bran sold (tons)

Capacity utilization rate (annual)Notes. Standard deviations of continuous variables are in parentheses. The total capacityof and the willingness-to-pay for all the milling machines at millers are reported.

36